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Sun Y, Keskinocak P, Steimle LN, Kovacs SD, Wassilak SG. Modeling the spread of circulating vaccine-derived poliovirus type 2 outbreaks and interventions: A case study of Nigeria. Vaccine X 2024; 18:100476. [PMID: 38617838 PMCID: PMC11011220 DOI: 10.1016/j.jvacx.2024.100476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 03/12/2024] [Accepted: 03/15/2024] [Indexed: 04/16/2024] Open
Abstract
Background Despite the successes of the Global Polio Eradication Initiative, substantial challenges remain in eradicating the poliovirus. The Sabin-strain (live-attenuated) virus in oral poliovirus vaccine (OPV) can revert to circulating vaccine-derived poliovirus (cVDPV) in under-vaccinated communities, regain neurovirulence and transmissibility, and cause paralysis outbreaks. Since the cessation of type 2-containing OPV (OPV2) in 2016, there have been cVDPV type 2 (cVDPV2) outbreaks in four out of six geographical World Health Organization regions, making these outbreaks a significant public health threat. Preparing for and responding to cVDPV2 outbreaks requires an updated understanding of how different factors, such as outbreak responses with the novel type of OPV2 (nOPV2) and the existence of under-vaccinated areas, affect the disease spread. Methods We built a differential-equation-based model to simulate the transmission of cVDPV2 following reversion of the Sabin-strain virus in prolonged circulation. The model incorporates vaccinations by essential (routine) immunization and supplementary immunization activities (SIAs), the immunity induced by different poliovirus vaccines, and the reversion process from Sabin-strain virus to cVDPV. The model's outcomes include weekly cVDPV2 paralytic case counts and the die-out date when cVDPV2 transmission stops. In a case study of Northwest and Northeast Nigeria, we fit the model to data on the weekly cVDPV2 case counts with onset in 2018-2021. We then used the model to test the impact of different outbreak response scenarios during a prediction period of 2022-2023. The response scenarios included no response, the planned response (based on Nigeria's SIA calendar), and a set of hypothetical responses that vary in the dates at which SIAs started. The planned response scenario included two rounds of SIAs that covered almost all areas of Northwest and Northeast Nigeria except some under-vaccinated areas (e.g., Sokoto). The hypothetical response scenarios involved two, three, and four rounds of SIAs that covered the whole Northwest and Northeast Nigeria. All SIAs in tested outbreak response scenarios used nOPV2. We compared the outcomes of tested outbreak response scenarios in the prediction period. Results Modeled cVDPV2 weekly case counts aligned spatiotemporally with the data. The prediction results indicated that implementing the planned response reduced total case counts by 79% compared to no response, but did not stop the transmission, especially in under-vaccinated areas. Implementing the hypothetical response scenarios involving two rounds of nOPV2 SIAs that covered all areas further reduced cVDPV2 case counts in under-vaccinated areas by 91-95% compared to the planned response, with greater impact from completing the two rounds at an earlier time, but it did not stop the transmission. When the first two rounds were completed in early April 2022, implementing two additional rounds stopped the transmission in late January 2023. When the first two rounds were completed six weeks earlier (i.e., in late February 2022), implementing one (two) additional round stopped the transmission in early February 2023 (late November 2022). The die out was always achieved last in the under-vaccinated areas of Northwest and Northeast Nigeria. Conclusions A differential-equation-based model of poliovirus transmission was developed and validated in a case study of Northwest and Northeast Nigeria. The results highlighted (i) the effectiveness of nOPV2 in reducing outbreak case counts; (ii) the need for more rounds of outbreak response SIAs that covered all of Northwest and Northeast Nigeria in 2022 to stop the cVDPV2 outbreaks; (iii) that persistent transmission in under-vaccinated areas delayed the progress towards stopping outbreaks; and (iv) that a quicker outbreak response would avert more paralytic cases and require fewer SIA rounds to stop the outbreaks.
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Affiliation(s)
- Yuming Sun
- H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Pinar Keskinocak
- H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Lauren N. Steimle
- H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA, USA
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Thompson KM, Kalkowska DA, Routh JA, Brenner IR, Rosenberg ES, Zucker JR, Langdon-Embry M, Sugerman DE, Burns CC, Badizadegan K. Modeling Poliovirus Transmission and Responses in New York State. J Infect Dis 2024; 229:1097-1106. [PMID: 37596838 PMCID: PMC11284859 DOI: 10.1093/infdis/jiad355] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 08/08/2023] [Accepted: 08/16/2023] [Indexed: 08/20/2023] Open
Abstract
BACKGROUND In July 2022, New York State (NYS) reported a case of paralytic polio in an unvaccinated young adult, and subsequent wastewater surveillance confirmed sustained local transmission of type 2 vaccine-derived poliovirus (VDPV2) in NYS with genetic linkage to the paralyzed patient. METHODS We adapted an established poliovirus transmission and oral poliovirus vaccine evolution model to characterize dynamics of poliovirus transmission in NYS, including consideration of the immunization activities performed as part of the declared state of emergency. RESULTS Despite sustained transmission of imported VDPV2 in NYS involving potentially thousands of individuals (depending on seasonality, population structure, and mixing assumptions) in 2022, the expected number of additional paralytic cases in years 2023 and beyond is small (less than 0.5). However, continued transmission and/or reintroduction of poliovirus into NYS and other populations remains a possible risk in communities that do not achieve and maintain high immunization coverage. CONCLUSIONS In countries such as the United States that use only inactivated poliovirus vaccine, even with high average immunization coverage, imported polioviruses may circulate and pose a small but nonzero risk of causing paralysis in nonimmune individuals.
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Affiliation(s)
| | | | - Janell A Routh
- Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - I Ravi Brenner
- Office of Public Health, New York State Department of Health, Albany, New York, USA
| | - Eli S Rosenberg
- Office of Public Health, New York State Department of Health, Albany, New York, USA
- Department of Epidemiology and Biostatistics, State University of New York at Albany, Albany, New York, USA
| | - Jane R Zucker
- New York City Department of Health and Mental Hygiene, New York, New York, USA
- Immunization Services Division, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | | | - David E Sugerman
- Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Cara C Burns
- Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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Thompson KM, Kalkowska DA, Kidd SE, Burns CC, Badizadegan K. Trade-offs of different poliovirus vaccine options for outbreak response in the United States and other countries that only use inactivated poliovirus vaccine (IPV) in routine immunization. Vaccine 2024; 42:819-827. [PMID: 38218668 PMCID: PMC10947589 DOI: 10.1016/j.vaccine.2023.12.081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 12/23/2023] [Accepted: 12/29/2023] [Indexed: 01/15/2024]
Abstract
Delays in achieving polio eradication have led to ongoing risks of poliovirus importations that may cause outbreaks in polio-free countries. Because of the low, but non-zero risk of paralysis with oral poliovirus vaccines (OPVs), countries that achieve and maintain high national routine immunization coverage have increasingly shifted to exclusive use of inactivated poliovirus vaccine (IPV) for all preventive immunizations. However, immunization coverage within countries varies, with under-vaccinated subpopulations potentially able to sustain transmission of imported polioviruses and experience local outbreaks. Due to its cost, ease-of-use, and ability to induce mucosal immunity, using OPV as an outbreak control measure offers a more cost-effective option in countries in which OPV remains in use. However, recent polio outbreaks in IPV-only countries raise questions about whether and when IPV use for outbreak response may fail to stop poliovirus transmission and what consequences may follow from using OPV for outbreak response in these countries. We systematically reviewed the literature to identify modeling studies that explored the use of IPV for outbreak response in IPV-only countries. In addition, applying a model of the 2022 type 2 poliovirus outbreak in New York, we characterized the implications of using different OPV formulations for outbreak response instead of IPV. We also explored the hypothetical scenario of the same outbreak except for type 1 poliovirus instead of type 2. We find that using IPV for outbreak response will likely only stop outbreaks for polioviruses of relatively low transmission potential in countries with very high overall immunization coverage, seasonal transmission dynamics, and only if IPV immunization interventions reach some unvaccinated individuals. Using OPV for outbreak response in IPV-only countries poses substantial risks and challenges that require careful consideration, but may represent an option to consider for some outbreaks in some populations depending on the properties of the available vaccines and coverage attainable.
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Affiliation(s)
| | | | - Sarah E Kidd
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Cara C Burns
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
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Thompson KM, Badizadegan K. Evolution of global polio eradication strategies: targets, vaccines, and supplemental immunization activities (SIAs). Expert Rev Vaccines 2024; 23:597-613. [PMID: 38813792 DOI: 10.1080/14760584.2024.2361060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 05/24/2024] [Indexed: 05/31/2024]
Abstract
BACKGROUND Despite multiple revisions of targets and timelines in polio eradication plans since 1988, including changes in supplemental immunization activities (SIAs) that increase immunity above routine immunization (RI) coverage, poliovirus transmission continues as of 2024. METHODS We reviewed polio eradication plans and Global Polio Eradication Initiative (GPEI) annual reports and budgets to characterize key phases of polio eradication, the evolution of poliovirus vaccines, and the role of SIAs. We used polio epidemiology to provide context for successes and failures and updated prior modeling to show the contribution of SIAs in achieving and maintaining low polio incidence compared to expected incidence for the counterfactual of RI only. RESULTS We identified multiple phases of polio eradication that included shifts in targets and timelines and the introduction of different poliovirus vaccines, which influenced polio epidemiology. Notable shifts occurred in GPEI investments in SIAs since 2001, particularly since 2016. Modeling results suggest that SIAs play(ed) a key role in increasing (and maintaining) high population immunity to levels required to eradicate poliovirus transmission globally. CONCLUSIONS Shifts in polio eradication strategy and poliovirus vaccine usage in SIAs provide important context for understanding polio epidemiology, delayed achievement of polio eradication milestones, and complexity of the polio endgame.
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Badizadegan K, Kalkowska DA, Thompson KM. Health Economic Analysis of Antiviral Drugs in the Global Polio Eradication Endgame. Med Decis Making 2023; 43:850-862. [PMID: 37577803 PMCID: PMC10680042 DOI: 10.1177/0272989x231191127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
BACKGROUND Polio antiviral drugs (PAVDs) may provide a critical tool in the eradication endgame by stopping poliovirus infections in immunodeficient individuals who may not clear the virus without therapeutic intervention. Although prolonged/chronic poliovirus excreters are rare, they represent a source of poliovirus reintroduction into the general population. Prior studies that assumed the successful cessation of all oral poliovirus vaccine (OPV) use estimated the potential upper bound of the incremental net benefits (INBs) of resource investments in research and development of PAVDs. However, delays in polio eradication, OPV cessation, and the development of PAVDs necessitate an updated economic analysis to reevaluate the costs and benefits of further investments in PAVDs. METHODS Using a global integrated model of polio transmission, immunity, vaccine dynamics, risks, and economics, we explore the risks of reintroduction of polio transmission due to immunodeficiency-related vaccine-derived poliovirus (iVDPV) excreters and reevaluate the upper bound of the INBs of PAVDs. RESULTS Under the current conditions, for which the use of OPV will likely continue for the foreseeable future, even with successful eradication of type 1 wild poliovirus by the end of 2023 and continued use of Sabin OPV for outbreak response, we estimate an upper bound INB of 60 million US$2019. With >100 million US$2019 already invested in PAVD development and with the introduction of novel OPVs that are less likely to revert to neurovirulence, our analysis suggests the expected INBs of PAVDs would not offset their costs. CONCLUSIONS While PAVDs could play an important role in the polio endgame, their expected economic benefits drop with ongoing OPV use and poliovirus transmissions. However, stakeholders may pursue the development of PAVDs as a desired product regardless of their economic benefits.HighlightsWhile polio antiviral drugs could play an important role in the polio endgame, their expected economic benefits continue to drop with delays in polio eradication and the continued use of oral poliovirus vaccines.The incremental net benefits of investments in polio antiviral drug development and screening for immunodeficiency-related circulating polioviruses are small.Limited global resources are better spent on increasing global population immunity to polioviruses to stop and prevent poliovirus transmission.
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Wong W, Gauld J, Famulare M. From vaccine to pathogen: Modeling Sabin 2 vaccine virus reversion and evolutionary epidemiology in Matlab, Bangladesh. Virus Evol 2023; 9:vead044. [PMID: 37692896 PMCID: PMC10491863 DOI: 10.1093/ve/vead044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 06/26/2023] [Accepted: 07/07/2023] [Indexed: 09/12/2023] Open
Abstract
The oral poliovirus vaccines (OPVs) are one of the most effective disease eradication tools in public health. However, the OPV strains are genetically unstable and can cause outbreaks of circulating, vaccine-derived Type 2 poliovirus (cVDPV2) that are clinically indistinguishable from wild poliovirus (WPV) outbreaks. Here, we developed a Sabin 2 reversion model that simulates the reversion of Sabin 2 to reacquire a WPV-like phenotype based on the clinical differences in shedding duration and infectiousness between individuals vaccinated with Sabin 2 and those infected with WPV. Genetic reversion is informed by a canonical reversion pathway defined by three gatekeeper mutations (A481G, U2909C, and U398C) and the accumulation of deleterious nonsynonymous mutations. Our model captures essential aspects of both phenotypic and molecular evolution and simulates transmission using a multiscale transmission model that consolidates the relationships among immunity, susceptibility, and transmission risk. Despite rapid Sabin 2 attenuation reversal, we show that the emergence of a revertant virus does not guarantee a cVDPV2 outbreak. When simulating outbreaks in Matlab, Bangladesh, we found that cVDPV2 outbreaks are most likely in areas with low population-level immunity and poor sanitation. In Matlab, our model predicted that declining immunity against Type 2 poliovirus following the cessation of routine OPV vaccination was not enough to promote cVDPV2 emergence. However, cVDPV2 emergencedepended on the average viral exposure dose per contact, which was modeled as a combination of the viral concentration per fecal gram and the average fecal-oral dose per contact. These results suggest that cVDPV2 emergence risk can be mitigated by reducing the amount of infectious fecal material individuals are exposed to. Thus, a combined strategy of assessing and improving sanitation levels in conjunction with high-coverage vaccination campaigns could limit the future cVDPV2 emergence.
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Affiliation(s)
- Wesley Wong
- Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, SPH 1, Boston, MA 02115, USA
| | - Jillian Gauld
- Institute for Disease Modeling, Bill and Melinda Gates Foundation, 500 5th Ave N, Seattle, WA 98109, USA
| | - Michael Famulare
- Institute for Disease Modeling, Bill and Melinda Gates Foundation, 500 5th Ave N, Seattle, WA 98109, USA
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Kalkowska DA, Badizadegan K, Thompson KM. Outbreak management strategies for cocirculation of multiple poliovirus types. Vaccine 2023:S0264-410X(23)00429-2. [PMID: 37121801 DOI: 10.1016/j.vaccine.2023.04.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 04/11/2023] [Indexed: 05/02/2023]
Abstract
Prior modeling studies showed that current outbreak management strategies are unlikely to stop outbreaks caused by type 1 wild polioviruses (WPV1) or circulating vaccine-derived polioviruses (cVDPVs) in many areas, and suggested increased risks of outbreaks with cocirculation of more than one type of poliovirus. The surge of type 2 poliovirus transmission that began in 2019 and continues to date, in conjunction with decreases in preventive supplemental immunization activities (SIAs) for poliovirus types 1 and 3, has led to the emergence of several countries with cocirculation of more than one type of poliovirus. Response to these emerging cocirculation events is theoretically straightforward, but the different formulations, types, and inventories of oral poliovirus vaccines (OPVs) available for outbreak response present challenging practical questions. In order to demonstrate the implications of using different vaccine options and outbreak campaign strategies, we applied a transmission model to a hypothetical population with conditions similar to populations currently experiencing outbreaks of cVDPVs of both types 1 and 2. Our results suggest prevention of the largest number of paralytic cases occurs when using (1) trivalent OPV (tOPV) (or coadministering OPV formulations for all three types) until one poliovirus outbreak type dies out, followed by (2) using a type-specific OPV until the remaining poliovirus outbreak type also dies out. Using tOPV first offers a lower overall expected cost, but this option may be limited by the willingness to expose populations to type 2 Sabin OPV strains. For strategies that use type 2 novel OPV (nOPV2) concurrently administered with bivalent OPV (bOPV, containing types 1 and 3 OPV) emerges as a leading option, but questions remain about feasibility, logistics, type-specific take rates, and coadministration costs.
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Kalkowska DA, Badizadegan K, Thompson KM. Modeling scenarios for ending poliovirus transmission in Pakistan and Afghanistan. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2023; 43:660-676. [PMID: 35739080 PMCID: PMC9780402 DOI: 10.1111/risa.13983] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Pakistan and Afghanistan pose risks for international transmission of polioviruses as the last global reservoir for wild poliovirus type 1 (WPV1) and a reservoir for type 2 circulating vaccine-derived polioviruses (cVDPV2s). Widespread transmission of WPV1 and cVDPV2 in 2019-2020 and resumption of intensive supplemental immunization activities (SIAs) in 2020-2021 using oral poliovirus vaccine (OPV) led to decreased transmission of WPV1 and cVDPV2 as of the end of 2021. Using an established dynamic disease transmission model, we explore multiple bounding scenarios with varying intensities of SIAs using bivalent OPV (bOPV) and/or trivalent tOPV (tOPV) to characterize potential die out of transmission. This analysis demonstrates potential sets of actions that may lead to elimination of poliovirus transmission in Pakistan and/or Afghanistan. Some modeled scenarios suggest that Pakistan and Afghanistan could increase population immunity to levels high enough to eliminate transmission, and if maintained, achieve WPV1 and cVDPV2 elimination as early as 2022. This requires intensive and proactive OPV SIAs to prevent transmission, instead of surveillance followed by reactive outbreak response. The reduction of cases observed in 2021 may lead to a false sense of security that polio has already or soon will die out on its own, but relaxation of immunization activities runs the risk of lowering population immunity to, or below, the minimum die-out threshold such that transmission continues. Transmission modeling may play a key role in managing expectations and supporting future modeling about the confidence of no virus circulation in anticipation of global certification decisions.
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Thompson KM, Kalkowska DA, Badizadegan K. Looking back at prospective modeling of outbreak response strategies for managing global type 2 oral poliovirus vaccine (OPV2) cessation. Front Public Health 2023; 11:1098419. [PMID: 37033033 PMCID: PMC10080024 DOI: 10.3389/fpubh.2023.1098419] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 03/03/2023] [Indexed: 04/11/2023] Open
Abstract
Introduction Detection of poliovirus transmission and ongoing oral poliovirus vaccine (OPV) use continue to delay poliomyelitis eradication. In 2016, the Global Polio Eradication Initiative (GPEI) coordinated global cessation of type 2 OPV (OPV2) for preventive immunization and limited its use to emergency outbreak response. In 2019, GPEI partners requested restart of some Sabin OPV2 production and also accelerated the development of a genetically modified novel OPV2 vaccine (nOPV2) that promised greater genetic stability than monovalent Sabin OPV2 (mOPV2). Methods We reviewed integrated risk, economic, and global poliovirus transmission modeling performed before OPV2 cessation, which recommended multiple risk management strategies to increase the chances of successfully ending all transmission of type 2 live polioviruses. Following OPV2 cessation, strategies implemented by countries and the GPEI deviated from model recommended risk management strategies. Complementing other modeling that explores prospective outbreak response options for improving outcomes for the current polio endgame trajectory, in this study we roll back the clock to 2017 and explore counterfactual trajectories that the polio endgame could have followed if GPEI had: (1) managed risks differently after OPV2 cessation and/or (2) developed nOPV2 before and used it exclusively for outbreak response after OPV2 cessation. Results The implementation of the 2016 model-based recommended outbreak response strategies could have ended (and could still substantially improve the probability of ending) type 2 poliovirus transmission. Outbreak response performance observed since 2016 would not have been expected to achieve OPV2 cessation with high confidence, even with the availability of nOPV2 prior to the 2016 OPV2 cessation. Discussion As implemented, the 2016 OPV2 cessation failed to stop type 2 transmission. While nOPV2 offers benefits of lower risk of seeding additional outbreaks, its reduced secondary spread relative to mOPV2 may imply relatively higher coverage needed for nOPV2 than mOPV2 to stop outbreaks.
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Thompson KM, Kalkowska DA, Badizadegan K. Health economic analysis of vaccine options for the polio eradication endgame: 2022-2036. Expert Rev Vaccines 2022; 21:1667-1674. [PMID: 36154436 PMCID: PMC10116513 DOI: 10.1080/14760584.2022.2128108] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND : Multiple vaccine options are available for polio prevention and risk management. Integrated global risk, economic, and poliovirus transmission modeling provides a tool to explore the dynamics of ending all use of one or more poliovirus vaccines to simplify the polio eradication endgame. RESEARCH DESIGN AND METHODS : With global reported cases of poliomyelitis trending higher since 2016, we apply an integrated global model to simulate prospective vaccine policies and strategies for OPV-using countries starting with initial conditions that correspond to the epidemiological poliovirus transmission situation at the beginning of 2022. RESULTS : Abruptly ending all OPV use in 2023 and relying only on IPV to prevent paralysis with current routine immunization coverage would lead to expected reestablished endemic transmission of poliovirus types 1 and 2, and approximately 150,000 expected cases of poliomyelitis per year. Alternatively, if OPV-using countries restart trivalent OPV (tOPV) use for all immunization activities and end IPV use, the model shows the lowest anticipated annual polio cases and lowest costs. CONCLUSIONS : Poor global risk management and coordination of OPV cessation remain a critical failure mode for the polio endgame, and national and global decision makers face difficult choices due to multiple available polio vaccine options and immunization strategies.
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Effect of Population Partitioning on the Probability of Silent Circulation of Poliovirus. Bull Math Biol 2022; 84:62. [PMID: 35507206 DOI: 10.1007/s11538-022-01014-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 03/21/2022] [Indexed: 11/02/2022]
Abstract
Polio can circulate unobserved in regions that are challenging to monitor. To assess the probability of silent circulation, simulation models can be used to understand transmission dynamics when detection is unreliable. Model assumptions, however, impact the estimated probability of silent circulation. Here, we examine the impact of having distinct populations, rather than a single well-mixed population, with a discrete-individual model including environmental surveillance. We show that partitioning a well-mixed population into networks of distinct communities may result in a higher probability of silent circulation as a result of the time it takes for the detection of a circulation event. Population structure should be considered when assessing polio control in a region with many loosely interacting communities.
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Brouwer AF, Eisenberg MC, Shulman LM, Famulare M, Koopman JS, Kroiss SJ, Hindiyeh M, Manor Y, Grotto I, Eisenberg JNS. The role of time-varying viral shedding in modelling environmental surveillance for public health: revisiting the 2013 poliovirus outbreak in Israel. J R Soc Interface 2022; 19:20220006. [PMID: 35582812 PMCID: PMC9114981 DOI: 10.1098/rsif.2022.0006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 04/06/2022] [Indexed: 12/17/2022] Open
Abstract
Environmental pathogen surveillance is a sensitive tool that can detect early-stage outbreaks, and it is being used to track poliovirus and other pathogens. However, interpretation of longitudinal environmental surveillance signals is difficult because the relationship between infection incidence and viral load in wastewater depends on time-varying shedding intensity. We developed a mathematical model of time-varying poliovirus shedding intensity consistent with expert opinion across a range of immunization states. Incorporating this shedding model into an infectious disease transmission model, we analysed quantitative, polymerase chain reaction data from seven sites during the 2013 Israeli poliovirus outbreak. Compared to a constant shedding model, our time-varying shedding model estimated a slower peak (four weeks later), with more of the population reached by a vaccination campaign before infection and a lower cumulative incidence. We also estimated the population shed virus for an average of 29 days (95% CI 28-31), longer than expert opinion had suggested for a population that was purported to have received three or more inactivated polio vaccine (IPV) doses. One explanation is that IPV may not substantially affect shedding duration. Using realistic models of time-varying shedding coupled with longitudinal environmental surveillance may improve our understanding of outbreak dynamics of poliovirus, SARS-CoV-2, or other pathogens.
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Affiliation(s)
- Andrew F. Brouwer
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | | | - Lester M. Shulman
- Central Virology Laboratory, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- School of Public Health, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | | | - James S. Koopman
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | | | - Musa Hindiyeh
- Central Virology Laboratory, Chaim Sheba Medical Center, Tel-Hashomer, Israel
| | - Yossi Manor
- Central Virology Laboratory, Chaim Sheba Medical Center, Tel-Hashomer, Israel
| | - Itamar Grotto
- Ministry of Health, Jerusalem, Israel
- Department of Public Health, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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Famulare M, Wong W, Haque R, Platts-Mills JA, Saha P, Aziz AB, Ahmed T, Islam MO, Uddin MJ, Bandyopadhyay AS, Yunus M, Zaman K, Taniuchi M. Multiscale model for forecasting Sabin 2 vaccine virus household and community transmission. PLoS Comput Biol 2021; 17:e1009690. [PMID: 34932560 PMCID: PMC8726461 DOI: 10.1371/journal.pcbi.1009690] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 01/04/2022] [Accepted: 11/29/2021] [Indexed: 11/19/2022] Open
Abstract
Since the global withdrawal of Sabin 2 oral poliovirus vaccine (OPV) from routine immunization, the Global Polio Eradication Initiative (GPEI) has reported multiple circulating vaccine-derived poliovirus type 2 (cVDPV2) outbreaks. Here, we generated an agent-based, mechanistic model designed to assess OPV-related vaccine virus transmission risk in populations with heterogeneous immunity, demography, and social mixing patterns. To showcase the utility of our model, we present a simulation of mOPV2-related Sabin 2 transmission in rural Matlab, Bangladesh based on stool samples collected from infants and their household contacts during an mOPV2 clinical trial. Sabin 2 transmission following the mOPV2 clinical trial was replicated by specifying multiple, heterogeneous contact rates based on household and community membership. Once calibrated, the model generated Matlab-specific insights regarding poliovirus transmission following an accidental point importation or mass vaccination event. We also show that assuming homogeneous contact rates (mass action), as is common of poliovirus forecast models, does not accurately represent the clinical trial and risks overestimating forecasted poliovirus outbreak probability. Our study identifies household and community structure as an important source of transmission heterogeneity when assessing OPV-related transmission risk and provides a calibratable framework for expanding these analyses to other populations. Trial Registration: ClinicalTrials.gov This trial is registered with clinicaltrials.gov, NCT02477046.
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Affiliation(s)
- Michael Famulare
- Institute for Disease Modeling, Global Good, Intellectual Ventures, Bellevue, Washington, United States of America
| | - Wesley Wong
- Institute for Disease Modeling, Global Good, Intellectual Ventures, Bellevue, Washington, United States of America
| | - Rashidul Haque
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - James A. Platts-Mills
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, United States of America
| | - Parimalendu Saha
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Asma B. Aziz
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Tahmina Ahmed
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Md Ohedul Islam
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Md Jashim Uddin
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, United States of America
| | | | - Mohammed Yunus
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Khalequ Zaman
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Mami Taniuchi
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, United States of America
- Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States of America
- Department of Engineering Systems and Environment, University of Virginia, Charlottesville, Virginia, United States of America
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14
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Decouttere C, De Boeck K, Vandaele N. Advancing sustainable development goals through immunization: a literature review. Global Health 2021; 17:95. [PMID: 34446050 PMCID: PMC8390056 DOI: 10.1186/s12992-021-00745-w] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 07/23/2021] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Immunization directly impacts health (SDG3) and brings a contribution to 14 out of the 17 Sustainable Development Goals (SDGs), such as ending poverty, reducing hunger, and reducing inequalities. Therefore, immunization is recognized to play a central role in reaching the SDGs, especially in low- and middle-income countries (LMICs). Despite continuous interventions to strengthen immunization systems and to adequately respond to emergency immunization during epidemics, the immunization-related indicators for SDG3 lag behind in sub-Saharan Africa. Especially taking into account the current Covid19 pandemic, the current performance on the connected SDGs is both a cause and a result of this. METHODS We conduct a literature review through a keyword search strategy complemented with handpicking and snowballing from earlier reviews. After title and abstract screening, we conducted a qualitative analysis of key insights and categorized them according to showing the impact of immunization on SDGs, sustainability challenges, and model-based solutions to these challenges. RESULTS We reveal the leveraging mechanisms triggered by immunization and position them vis-à-vis the SDGs, within the framework of Public Health and Planetary Health. Several challenges for sustainable control of vaccine-preventable diseases are identified: access to immunization services, global vaccine availability to LMICs, context-dependent vaccine effectiveness, safe and affordable vaccines, local/regional vaccine production, public-private partnerships, and immunization capacity/capability building. Model-based approaches that support SDG-promoting interventions concerning immunization systems are analyzed in light of the strategic priorities of the Immunization Agenda 2030. CONCLUSIONS In general terms, it can be concluded that relevant future research requires (i) design for system resilience, (ii) transdisciplinary modeling, (iii) connecting interventions in immunization with SDG outcomes, (iv) designing interventions and their implementation simultaneously, (v) offering tailored solutions, and (vi) model coordination and integration of services and partnerships. The research and health community is called upon to join forces to activate existing knowledge, generate new insights and develop decision-supporting tools for Low-and Middle-Income Countries' health authorities and communities to leverage immunization in its transformational role toward successfully meeting the SDGs in 2030.
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Affiliation(s)
- Catherine Decouttere
- KU Leuven, Access-To-Medicines research Center, Naamsestraat 69, Leuven, Belgium
| | - Kim De Boeck
- KU Leuven, Access-To-Medicines research Center, Naamsestraat 69, Leuven, Belgium
| | - Nico Vandaele
- KU Leuven, Access-To-Medicines research Center, Naamsestraat 69, Leuven, Belgium
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Thompson KM, Kalkowska DA, Badizadegan K. Hypothetical emergence of poliovirus in 2020: part 2. exploration of the potential role of vaccines in control and eradication. Expert Rev Vaccines 2021; 20:449-460. [PMID: 33599178 DOI: 10.1080/14760584.2021.1891889] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVES The emergence of human pathogens with pandemic potential motivates rapid vaccine development. We explore the role of vaccines in control and eradication of a novel emerging pathogen. METHODS We hypothetically simulate emergence of a novel wild poliovirus (nWPV) in 2020 assuming an immunologically naïve population. Assuming different nonpharmaceutical interventions (NPIs), we explore the impacts of vaccines resembling serotype-specific oral poliovirus vaccine (OPV), novel OPV (nOPV), or inactivated poliovirus vaccine (IPV). RESULTS Vaccines most effectively change the trajectory of an emerging disease when disseminated early, rapidly, and widely in the background of ongoing strict NPIs, unless the NPIs successfully eradicate the emerging pathogen before it establishes endemic transmission. Without strict NPIs, vaccines primarily reduce the burden of disease in the remaining susceptible individuals and in new birth cohorts. Live virus vaccines that effectively compete with the nWPVs can reduce disease burdens more than other vaccines. When relaxation of existing NPIs occurs at the time of vaccine introduction, nWPV transmission can counterintuitively increase in the short term. CONCLUSIONS Vaccines can increase the probability of disease eradication in the context of strict NPIs. However, successful eradication will depend on specific immunization strategies used and a global commitment to eradication.
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Thompson KM, Kalkowska DA, Badizadegan K. A Health Economic Analysis for Oral Poliovirus Vaccine to Prevent COVID-19 in the United States. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2021; 41:376-386. [PMID: 33084153 PMCID: PMC7983986 DOI: 10.1111/risa.13614] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 10/07/2020] [Indexed: 05/20/2023]
Abstract
COVID-19 led to a recent high-profile proposal to reintroduce oral poliovirus vaccine (OPV) in the United States (U.S.), initially in clinical trials, but potentially for widespread and repeated use. We explore logistical challenges related to U.S. OPV administration in 2020, review the literature related to nonspecific effects of OPV to induce innate immunity, and model the health and economic implications of the proposal. The costs of reintroducing a single OPV dose to 331 million Americans would exceed $4.4 billion. Giving a dose of bivalent OPV to the entire U.S. population would lead to an expected 40 identifiable cases of vaccine-associated paralytic polio, with young Americans at the highest risk. Reintroducing any OPV use in the U.S. poses a risk of restarting transmission of OPV-related viruses and could lead to new infections in immunocompromised individuals with B-cell related primary immunodeficiencies that could lead to later cases of paralysis. Due to the lack of a currently licensed OPV in the U.S., the decision to administer OPV to Americans for nonspecific immunological effects would require purchasing limited global OPV supplies that could impact polio eradication efforts. Health economic modeling suggests no role for reintroducing OPV into the U.S. with respect to responding to COVID-19. Countries that currently use OPV experience fundamentally different risks, costs, and benefits than the U.S. Successful global polio eradication will depend on sufficient OPV supplies, achieving and maintaining high OPV coverage in OPV-using countries, and effective global OPV cessation and containment in all countries, including the U.S.
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Kalkowska DA, Pallansch MA, Wilkinson A, Bandyopadhyay AS, Konopka-Anstadt JL, Burns CC, Oberste MS, Wassilak SGF, Badizadegan K, Thompson KM. Updated Characterization of Outbreak Response Strategies for 2019-2029: Impacts of Using a Novel Type 2 Oral Poliovirus Vaccine Strain. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2021; 41:329-348. [PMID: 33174263 PMCID: PMC7887065 DOI: 10.1111/risa.13622] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 10/08/2020] [Accepted: 10/16/2020] [Indexed: 05/06/2023]
Abstract
Delays in achieving the global eradication of wild poliovirus transmission continue to postpone subsequent cessation of all oral poliovirus vaccine (OPV) use. Countries must stop OPV use to end all cases of poliomyelitis, including vaccine-associated paralytic polio (VAPP) and cases caused by vaccine-derived polioviruses (VDPVs). The Global Polio Eradication Initiative (GPEI) coordinated global cessation of all type 2 OPV (OPV2) use in routine immunization in 2016 but did not successfully end the transmission of type 2 VDPVs (VDPV2s), and consequently continues to use type 2 OPV (OPV2) for outbreak response activities. Using an updated global poliovirus transmission and OPV evolution model, we characterize outbreak response options for 2019-2029 related to responding to VDPV2 outbreaks with a genetically stabilized novel OPV (nOPV2) strain or with the currently licensed monovalent OPV2 (mOPV2). Given uncertainties about the properties of nOPV2, we model different assumptions that appear consistent with the evidence on nOPV2 to date. Using nOPV2 to respond to detected cases may reduce the expected VDPV and VAPP cases and the risk of needing to restart OPV2 use in routine immunization compared to mOPV2 use for outbreak response. The actual properties, availability, and use of nOPV2 will determine its effects on type 2 poliovirus transmission in populations. Even with optimal nOPV2 performance, countries and the GPEI would still likely need to restart OPV2 use in routine immunization in OPV-using countries if operational improvements in outbreak response to stop the transmission of cVDPV2s are not implemented effectively.
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Affiliation(s)
| | - Mark A. Pallansch
- National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Amanda Wilkinson
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | | | - Jennifer L. Konopka-Anstadt
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Cara C. Burns
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - M. Steven Oberste
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Steven G. F. Wassilak
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
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18
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Thompson KM, Kalkowska DA. Reflections on Modeling Poliovirus Transmission and the Polio Eradication Endgame. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2021; 41:229-247. [PMID: 32339327 PMCID: PMC7983882 DOI: 10.1111/risa.13484] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 03/27/2020] [Accepted: 03/27/2020] [Indexed: 05/06/2023]
Abstract
The Global Polio Eradication Initiative (GPEI) partners engaged modelers during the past nearly 20 years to support strategy and policy discussions and decisions, and to provide estimates of the risks, costs, and benefits of different options for managing the polio endgame. Limited efforts to date provided insights related to the validation of the models used for GPEI strategy and policy decisions. However, modeling results only influenced decisions in some cases, with other factors carrying more weight in many key decisions. In addition, the results from multiple modeling groups do not always agree, which supports selection of some strategies and/or policies counter to the recommendations from some modelers but not others. This analysis reflects on our modeling, and summarizes our premises and recommendations, the outcomes of these recommendations, and the implications of key limitations of models with respect to polio endgame strategy. We briefly review the current state of the GPEI given epidemiological experience as of early 2020, which includes failure of the GPEI to deliver on the objectives of its 2013-2018 strategic plan despite full financial support. Looking ahead, we provide context for why the GPEI strategy of global oral poliovirus vaccine (OPV) cessation to end all cases of poliomyelitis looks infeasible given the current state of the GPEI and the failure to successfully stop all transmission of serotype 2 live polioviruses within four years of the April-May 2016 coordinated cessation of serotype 2 OPV use in routine immunization.
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19
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Kalkowska DA, Pallansch MA, F. Wassilak SG, Cochi SL, Thompson KM. Global Transmission of Live Polioviruses: Updated Dynamic Modeling of the Polio Endgame. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2021; 41:248-265. [PMID: 31960533 PMCID: PMC7787008 DOI: 10.1111/risa.13447] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 10/30/2019] [Accepted: 12/02/2019] [Indexed: 05/05/2023]
Abstract
Nearly 20 years after the year 2000 target for global wild poliovirus (WPV) eradication, live polioviruses continue to circulate with all three serotypes posing challenges for the polio endgame. We updated a global differential equation-based poliovirus transmission and stochastic risk model to include programmatic and epidemiological experience through January 2020. We used the model to explore the likely dynamics of poliovirus transmission for 2019-2023, which coincides with a new Global Polio Eradication Initiative Strategic Plan. The model stratifies the global population into 72 blocks, each containing 10 subpopulations of approximately 10.7 million people. Exported viruses go into subpopulations within the same block and within groups of blocks that represent large preferentially mixing geographical areas (e.g., continents). We assign representative World Bank income levels to the blocks along with polio immunization and transmission assumptions, which capture some of the heterogeneity across countries while still focusing on global poliovirus transmission dynamics. We also updated estimates of reintroduction risks using available evidence. The updated model characterizes transmission dynamics and resulting polio cases consistent with the evidence through 2019. Based on recent epidemiological experience and prospective immunization assumptions for the 2019-2023 Strategic Plan, the updated model does not show successful eradication of serotype 1 WPV by 2023 or successful cessation of oral poliovirus vaccine serotype 2-related viruses.
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Affiliation(s)
| | - Mark A. Pallansch
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Steven G. F. Wassilak
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Stephen L. Cochi
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
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20
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Kalkowska DA, Franka R, Higgins J, Kovacs SD, Forbi JC, Wassilak SG, Pallansch MA, Thompson KM. Modeling Poliovirus Transmission in Borno and Yobe, Northeast Nigeria. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2021; 41:289-302. [PMID: 32348621 PMCID: PMC7814397 DOI: 10.1111/risa.13485] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/18/2020] [Accepted: 03/27/2020] [Indexed: 05/05/2023]
Abstract
Beginning in 2013, multiple local government areas (LGAs) in Borno and Yobe in northeast Nigeria and other parts of the Lake Chad basin experienced a violent insurgency that resulted in substantial numbers of isolated and displaced people. Northeast Nigeria represents the last known reservoir country of wild poliovirus (WPV) transmission in Africa, with detection of paralytic cases caused by serotype 1 WPV in 2016 in Borno and serotype 3 WPV in late 2012. Parts of Borno and Yobe are also problematic areas for transmission of serotype 2 circulating vaccine-derived polioviruses, and they continue to face challenges associated with conflict and inadequate health services in security-compromised areas that limit both immunization and surveillance activities. We model poliovirus transmission of all three serotypes for Borno and Yobe using a deterministic differential equation-based model that includes four subpopulations to account for limitations in access to immunization services and dynamic restrictions in population mixing. We find that accessibility issues and insufficient immunization allow for prolonged poliovirus transmission and potential undetected paralytic cases, although as of the end of 2019, including responsive program activities in the modeling suggest die out of indigenous serotypes 1 and 3 WPVs prior to 2020. Specifically, recent and current efforts to access isolated populations and provide oral poliovirus vaccine continue to reduce the risks of sustained and undetected transmission, although some uncertainty remains. Continued improvement in immunization and surveillance in the isolated subpopulations should minimize these risks. Stochastic modeling can build on this analysis to characterize the implications for undetected transmission and confidence about no circulation.
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Affiliation(s)
| | - Richard Franka
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Jeff Higgins
- Geospatial Research, Analysis and Services Program, Agency for Toxic Substances and Disease Registry, Atlanta, GA, USA
| | - Stephanie D. Kovacs
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Joseph C. Forbi
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Steven G.F Wassilak
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Mark A. Pallansch
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Kimberly M. Thompson
- Kid Risk, Inc., 7512 Dr. Phillips Blvd. #50-523 Orlando, FL 32819
- Corresponding author:
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21
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Kalkowska DA, Thompson KM. Health and Economic Outcomes Associated with Polio Vaccine Policy Options: 2019-2029. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2021; 41:364-375. [PMID: 33590519 PMCID: PMC7895457 DOI: 10.1111/risa.13664] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 12/04/2020] [Indexed: 05/08/2023]
Abstract
The polio endgame remains complicated, with many questions about future polio vaccines and national immunization policies. We simulated possible future poliovirus vaccine routine immunization policies for countries stratified by World Bank Income Levels and estimated the expected costs and cases using an updated integrated dynamic poliovirus transmission, stochastic risk, and economic model. We consider two reference cases scenarios: one that achieves the eradication of all wild polioviruses (WPVs) by 2023 and one in which serotype 1 WPV (WPV1) transmission continues. The results show that the addition of inactivated poliovirus vaccine (IPV) to routine immunization in all countries substantially increased the expected costs of the polio endgame, without substantially increasing its expected health or economic benefits. Adding a second dose of IPV to the routine immunization schedules of countries that currently include a single IPV dose further increases costs and does not appear economically justified in the reference case that does not stop WPV transmission. For the reference case that includes all WPV eradication, adding a second IPV dose at the time of successful oral poliovirus vaccine (OPV) cessation represents a cost-effective option. The risks and costs of needing to restart OPV use change the economics of the polio endgame, although the time horizon used for modeling impacts the overall economic results. National health leaders will want to consider the expected health and economic net benefits of their national polio vaccine strategies recognizing that preferred strategies may differ.
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Thompson KM, Kalkowska DA. Review of poliovirus modeling performed from 2000 to 2019 to support global polio eradication. Expert Rev Vaccines 2020; 19:661-686. [PMID: 32741232 PMCID: PMC7497282 DOI: 10.1080/14760584.2020.1791093] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 06/22/2020] [Indexed: 01/03/2023]
Abstract
INTRODUCTION Over the last 20 years (2000-2019) the partners of the Global Polio Eradication Initiative (GPEI) invested in the development and application of mathematical models of poliovirus transmission as well as economics, policy, and risk analyses of polio endgame risk management options, including policies related to poliovirus vaccine use during the polio endgame. AREAS COVERED This review provides a historical record of the polio studies published by the three modeling groups that primarily performed the bulk of this work. This review also systematically evaluates the polio transmission and health economic modeling papers published in English in peer-reviewed journals from 2000 to 2019, highlights differences in approaches and methods, shows the geographic coverage of the transmission modeling performed, identified common themes, and discusses instances of similar or conflicting insights or recommendations. EXPERT OPINION Polio modeling performed during the last 20 years substantially impacted polio vaccine choices, immunization policies, and the polio eradication pathway. As the polio endgame continues, national preferences for polio vaccine formulations and immunization strategies will likely continue to change. Future modeling will likely provide important insights about their cost-effectiveness and their relative benefits with respect to controlling polio and potentially achieving and maintaining eradication.
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23
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Cheng E, Gambhirrao N, Patel R, Zhowandai A, Rychtář J, Taylor D. A game-theoretical analysis of poliomyelitis vaccination. J Theor Biol 2020; 499:110298. [PMID: 32371008 DOI: 10.1016/j.jtbi.2020.110298] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 04/21/2020] [Accepted: 04/26/2020] [Indexed: 12/15/2022]
Abstract
Poliomyelitis is a worldwide disease that has nearly been eradicated thanks to the Global Polio Eradication Initiative. Nevertheless, the disease is currently still endemic in three countries. In this paper, we incorporate the vaccination in a two age-class model of polio dynamics. Our main objective is to see whether mandatory vaccination policy is needed or if polio could be almost eradicated by a voluntary vaccination. We perform game theoretical analysis and compare the herd immunity vaccination levels with the Nash equilibrium vaccination levels. We show that the gap between two vaccination levels is too large. We conclude that the mandatory vaccination policy is therefore needed to achieve a complete eradication.
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Affiliation(s)
- Emily Cheng
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284-3068, USA.
| | - Neeha Gambhirrao
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284-3068, USA.
| | - Rohani Patel
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23284-3068, USA.
| | - Aufia Zhowandai
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284-2012, USA.
| | - Jan Rychtář
- Department of Mathematics and Applied Mathematics, Virginia Commonwealth University, Richmond, VA 23284-2014, USA.
| | - Dewey Taylor
- Department of Mathematics and Applied Mathematics, Virginia Commonwealth University, Richmond, VA 23284-2014, USA.
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Thompson KM, Kalkowska DA. Logistical challenges and assumptions for modeling the failure of global cessation of oral poliovirus vaccine (OPV). Expert Rev Vaccines 2019; 18:725-736. [PMID: 31248293 PMCID: PMC6816497 DOI: 10.1080/14760584.2019.1635463] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 06/20/2019] [Indexed: 12/27/2022]
Abstract
Introduction: The inability to successfully stop all use of oral poliovirus vaccine (OPV) as part of the polio endgame and/or the possibilities of reintroduction of live polioviruses after successful OPV cessation may imply the need to restart OPV production and use, either temporarily or permanently. Areas covered: Complementing prior work that explored the risks of potential OPV restart, we discuss the logistical challenges and implications of restarting OPV in the future, and we develop appropriate assumptions for modeling the possibility of OPV restart. The complexity of phased cessation of the three OPV serotypes implies different potential combinations of OPV use long term. We explore the complexity of polio vaccine choices and key unresolved policy questions that may impact continuing and future use of OPV and/or inactivated poliovirus vaccine (IPV). We then characterize the assumptions required to quantitatively model OPV restart in prospective global-integrated economic policy models for the polio endgame. Expert commentary: Depending on the timing, restarting production of OPV would imply some likely delays associated with ramp-up, re-licensing, and other logistics that would impact the availability and costs of restarting the use of OPV in national immunization programs after globally coordinated cessation of one or more OPV serotypes.
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25
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Brouwer AF, Masters NB, Eisenberg JNS. Quantitative Microbial Risk Assessment and Infectious Disease Transmission Modeling of Waterborne Enteric Pathogens. Curr Environ Health Rep 2019; 5:293-304. [PMID: 29679300 DOI: 10.1007/s40572-018-0196-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE OF REVIEW Waterborne enteric pathogens remain a global health threat. Increasingly, quantitative microbial risk assessment (QMRA) and infectious disease transmission modeling (IDTM) are used to assess waterborne pathogen risks and evaluate mitigation. These modeling efforts, however, have largely been conducted independently for different purposes and in different settings. In this review, we examine the settings where each modeling strategy is employed. RECENT FINDINGS QMRA research has focused on food contamination and recreational water in high-income countries (HICs) and drinking water and wastewater in low- and middle-income countries (LMICs). IDTM research has focused on large outbreaks (predominately LMICs) and vaccine-preventable diseases (LMICs and HICs). Human ecology determines the niches that pathogens exploit, leading researchers to focus on different risk assessment research strategies in different settings. To enhance risk modeling, QMRA and IDTM approaches should be integrated to include dynamics of pathogens in the environment and pathogen transmission through populations.
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Affiliation(s)
- Andrew F Brouwer
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Nina B Masters
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, 48109, USA
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Kalkowska DA, Duintjer Tebbens RJ, Pallansch MA, Thompson KM. Modeling Undetected Live Poliovirus Circulation After Apparent Interruption of Transmission: Pakistan and Afghanistan. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2019; 39:402-413. [PMID: 30296340 PMCID: PMC7842182 DOI: 10.1111/risa.13214] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Since most poliovirus infections occur with no paralytic symptoms, the possibility of silent circulation complicates the confirmation of the end of poliovirus transmission. Based on empirical field experience and theoretical modeling results, the Global Polio Eradication Initiative identified three years without observing paralytic cases from wild polioviruses with good acute flaccid paralysis surveillance as an indication of sufficient confidence that poliovirus circulation stopped. The complexities of real populations and the imperfect nature of real surveillance systems subsequently demonstrated the importance of specific modeling for areas at high risk of undetected circulation, resulting in varying periods of time required to obtain the same level of confidence about no undetected circulation. Using a poliovirus transmission model that accounts for variability in transmissibility and neurovirulence for different poliovirus serotypes and characterizes country-specific factors (e.g., vaccination and surveillance activities, demographics) related to wild and vaccine-derived poliovirus transmission in Pakistan and Afghanistan, we consider the probability of undetected poliovirus circulation for those countries once apparent die-out occurs (i.e., in the absence of any epidemiological signals). We find that gaps in poliovirus surveillance or reaching elimination with borderline sufficient population immunity could significantly increase the time to reach high confidence about interruption of live poliovirus transmission, such that the path taken to achieve and maintain poliovirus elimination matters. Pakistan and Afghanistan will need to sustain high-quality surveillance for polioviruses after apparent interruption of transmission and recognize that as efforts to identify cases or circulating live polioviruses decrease, the risks of undetected circulation increase and significantly delay the global polio endgame.
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Affiliation(s)
| | | | - Mark A Pallansch
- Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
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Duintjer Tebbens RJ, Thompson KM. Evaluation of Proactive and Reactive Strategies for Polio Eradication Activities in Pakistan and Afghanistan. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2019; 39:389-401. [PMID: 30239026 PMCID: PMC7857157 DOI: 10.1111/risa.13194] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 08/21/2018] [Accepted: 08/24/2018] [Indexed: 05/21/2023]
Abstract
Only Pakistan and Afghanistan reported any polio cases caused by serotype 1 wild polioviruses (WPV1s) in 2017. With the dwindling cases in both countries and pressure to finish eradication with the least possible resources, a danger exists of inappropriate prioritization of efforts between the two countries and insufficient investment in the two countries to finish the job. We used an existing differential-equation-based poliovirus transmission and oral poliovirus (OPV) evolution model to simulate a proactive strategy to stop transmission, and different hypothetical reactive strategies that adapt the quality of supplemental immunization activities (SIAs) in response to observed polio cases in Pakistan and Afghanistan. To account for the delay in perception and adaptation, we related the coverage of the SIAs in high-risk, undervaccinated subpopulations to the perceived (i.e., smoothed) polio incidence. Continuation of the current frequency and quality of SIAs remains insufficient to eradicate WPV1 in Pakistan and Afghanistan. Proactive strategies that significantly improve and sustain SIA quality lead to WPV1 eradication and the prevention of circulating vaccine-derived poliovirus (cVDPV) outbreaks. Reactive vaccination efforts that adapt moderately quickly and independently to changes in polio incidence in each country may succeed in WPV1 interruption after several cycles of outbreaks, or may interrupt WPV1 transmission in one country but subsequently import WPV1 from the other country or enable the emergence of cVDPV outbreaks. Reactive vaccination efforts that adapt independently and either more rapidly or more slowly to changes in polio incidence in each country may similarly fail to interrupt WPV1 transmission and result in oscillations of the incidence. Reactive strategies that divert resources to the country of highest priority may lead to alternating large outbreaks. Achieving WPV1 eradication and subsequent successful OPV cessation in Pakistan and Afghanistan requires proactive and sustained efforts to improve vaccination intensity in under-vaccinated subpopulations while maintaining high population immunity elsewhere.
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Kalkowska DA, Duintjer Tebbens RJ, Thompson KM. Environmental Surveillance System Characteristics and Impacts on Confidence About No Undetected Serotype 1 Wild Poliovirus Circulation. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2019; 39:414-425. [PMID: 30239023 PMCID: PMC7857156 DOI: 10.1111/risa.13193] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Surveillance for poliovirus during the polio endgame remains uncertain. Building on prior modeling of the potential for undetected poliovirus transmission for conditions like those in Pakistan and Afghanistan, we use a hypothetical model to explore several key characteristics of the poliovirus environmental surveillance (ES) system (e.g., number and quality of sites, catchment sizes, and sampling frequency) and characterize their impacts on the time required to reach high (i.e., 95%) confidence about no circulation (CNC95%) following the last detected case of serotype 1 wild poliovirus. The nature and quality of the existing and future acute flaccid paralysis (AFP) surveillance and ES system significantly impact the estimated CNC95% for places like Pakistan and Afghanistan. The analysis illustrates the tradeoffs between number of sites, sampling frequency, and catchments sizes, and suggests diminishing returns of increasing these three factors beyond a point that depends on site quality and the location of sites. Limitations in data quality and the hypothetical nature of the model reduce the ability to assess the extent to which actual ES systems offer benefits that exceed their costs. Thus, although poliovirus ES may help to reduce the time required to reach high confidence about the absence of undetected circulation, the effect strongly depends on the ability to establish effective ES sites in high-risk areas. The costs and benefits of ES require further analysis.
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Duintjer Tebbens RJ, Kalkowska DA, Thompson KM. Global certification of wild poliovirus eradication: insights from modelling hard-to-reach subpopulations and confidence about the absence of transmission. BMJ Open 2019; 9:e023938. [PMID: 30647038 PMCID: PMC6340450 DOI: 10.1136/bmjopen-2018-023938] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 11/29/2018] [Accepted: 11/30/2018] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVE To explore the extent to which undervaccinated subpopulations may influence the confidence about no circulation of wild poliovirus (WPV) after the last detected case. DESIGN AND PARTICIPANTS We used a hypothetical model to examine the extent to which the existence of an undervaccinated subpopulation influences the confidence about no WPV circulation after the last detected case as a function of different characteristics of the subpopulation (eg, size, extent of isolation). We also used the hypothetical population model to inform the bounds on the maximum possible time required to reach high confidence about no circulation in a completely isolated and unvaccinated subpopulation starting either at the endemic equilibrium or with a single infection in an entirely susceptible population. RESULTS It may take over 3 years to reach 95% confidence about no circulation for this hypothetical population despite high surveillance sensitivity and high vaccination coverage in the surrounding general population if: (1) ability to detect cases in the undervaccinated subpopulation remains exceedingly small, (2) the undervaccinated subpopulation remains small and highly isolated from the general population and (3) the coverage in the undervaccinated subpopulation remains very close to the minimum needed to eradicate. Fully-isolated hypothetical populations of 4000 people or less cannot sustain endemic transmission for more than 5 years, with at least 20 000 people required for a 50% chance of at least 5 years of sustained transmission in a population without seasonality that starts at the endemic equilibrium. Notably, however, the population size required for persistent transmission increases significantly for realistic populations that include some vaccination and seasonality and/or that do not begin at the endemic equilibrium. CONCLUSIONS Significant trade-offs remain inherent in global polio certification decisions, which underscore the need for making and valuing investments to maximise population immunity and surveillance quality in all remaining possible WPV reservoirs.
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Epidemiology of the silent polio outbreak in Rahat, Israel, based on modeling of environmental surveillance data. Proc Natl Acad Sci U S A 2018; 115:E10625-E10633. [PMID: 30337479 DOI: 10.1073/pnas.1808798115] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Israel experienced an outbreak of wild poliovirus type 1 (WPV1) in 2013-2014, detected through environmental surveillance of the sewage system. No cases of acute flaccid paralysis were reported, and the epidemic subsided after a bivalent oral polio vaccination (bOPV) campaign. As we approach global eradication, polio will increasingly be detected only through environmental surveillance. We developed a framework to convert quantitative polymerase chain reaction (qPCR) cycle threshold data into scaled WPV1 and OPV1 concentrations for inference within a deterministic, compartmental infectious disease transmission model. We used this approach to estimate the epidemic curve and transmission dynamics, as well as assess alternate vaccination scenarios. Our analysis estimates the outbreak peaked in late June, much earlier than previous estimates derived from analysis of stool samples, although the exact epidemic trajectory remains uncertain. We estimate the basic reproduction number was 1.62 (95% CI 1.04-2.02). Model estimates indicate that 59% (95% CI 9-77%) of susceptible individuals (primarily children under 10 years old) were infected with WPV1 over a little more than six months, mostly before the vaccination campaign onset, and that the vaccination campaign averted 10% (95% CI 1-24%) of WPV1 infections. As we approach global polio eradication, environmental monitoring with qPCR can be used as a highly sensitive method to enhance disease surveillance. Our analytic approach brings public health relevance to environmental data that, if systematically collected, can guide eradication efforts.
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Duintjer Tebbens RJ, Kalkowsa DA, Thompson KM. Poliovirus containment risks and their management. Future Virol 2018; 13:617-628. [PMID: 33598044 PMCID: PMC7885305 DOI: 10.2217/fvl-2018-0079] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 06/20/2018] [Indexed: 11/21/2022]
Abstract
AIM Assess risks related to breaches of poliovirus containment. METHOD Using a dynamic transmission model, we explore the variability among different populations in the vulnerability to poliovirus containment breaches as population immunity to transmission declines after oral poliovirus vaccine (OPV) cessation. RESULTS Although using OPV instead of wild poliovirus (WPV) seed strains for inactivated poliovirus vaccine (IPV) production offers some expected risk reintroduction of live polioviruses from IPV manufacturing facilities, OPV seed strain releases may become a significant threat within 5-10 years of OPV cessation in areas most conducive to fecal-oral poliovirus transmission, regardless of IPV use. CONCLUSIONS Efforts to quantify the risks demonstrate the challenges associated with understanding and managing relatively low-probability and high-consequence containment failure events.
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Duintjer Tebbens RJ, Thompson KM. Polio endgame risks and the possibility of restarting the use of oral poliovirus vaccine. Expert Rev Vaccines 2018; 17:739-751. [PMID: 30056767 PMCID: PMC6168953 DOI: 10.1080/14760584.2018.1506333] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/26/2018] [Indexed: 11/17/2022]
Abstract
INTRODUCTION Ending all cases of poliomyelitis requires successful cessation of all oral poliovirus vaccine (OPV), but the Global Polio Eradication Initiative (GPEI) partners should consider the possibility of an OPV restart. AREAS COVERED We review the risks of continued live poliovirus transmission after OPV cessation and characterize events that led to OPV restart in a global model that focused on identifying optimal strategies for OPV cessation and the polio endgame. Numerous different types of events that occurred since the globally coordinated cessation of serotype 2-containing OPV in 2016 highlight the possibility of continued outbreaks after homotypic OPV cessation. Modeling suggests a high risk of uncontrolled outbreaks once more than around 5,000 homotypic polio cases occur after cessation of an OPV serotype, at which point restarting OPV would become necessary to protect most populations. Current efforts to sunset the GPEI and transition its responsibilities to national governments poses risks that may limit the ability to implement management strategies needed to minimize the probability of an OPV restart. EXPERT COMMENTARY OPV restart remains a real possibility, but risk management choices made by the GPEI partners and national governments can reduce the risks of this low-probability but high-consequence event.
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Duintjer Tebbens RJ, Pallansch MA, Cochi SL, Ehrhardt D, Farag N, Hadler S, Hampton LM, Martinez M, Wassilak SG, Thompson KM. Modeling Poliovirus Transmission in Pakistan and Afghanistan to Inform Vaccination Strategies in Undervaccinated Subpopulations. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2018; 38:1701-1717. [PMID: 29314143 PMCID: PMC7879700 DOI: 10.1111/risa.12962] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 11/18/2017] [Accepted: 11/22/2017] [Indexed: 05/11/2023]
Abstract
Due to security, access, and programmatic challenges in areas of Pakistan and Afghanistan, both countries continue to sustain indigenous wild poliovirus (WPV) transmission and threaten the success of global polio eradication and oral poliovirus vaccine (OPV) cessation. We fitted an existing differential-equation-based poliovirus transmission and OPV evolution model to Pakistan and Afghanistan using four subpopulations to characterize the well-vaccinated and undervaccinated subpopulations in each country. We explored retrospective and prospective scenarios for using inactivated poliovirus vaccine (IPV) in routine immunization or supplemental immunization activities (SIAs). The undervaccinated subpopulations sustain the circulation of serotype 1 WPV and serotype 2 circulating vaccine-derived poliovirus. We find a moderate impact of past IPV use on polio incidence and population immunity to transmission mainly due to (1) the boosting effect of IPV for individuals with preexisting immunity from a live poliovirus infection and (2) the effect of IPV-only on oropharyngeal transmission for individuals without preexisting immunity from a live poliovirus infection. Future IPV use may similarly yield moderate benefits, particularly if access to undervaccinated subpopulations dramatically improves. However, OPV provides a much greater impact on transmission and the incremental benefit of IPV in addition to OPV remains limited. This study suggests that despite the moderate effect of using IPV in SIAs, using OPV in SIAs remains the most effective means to stop transmission, while limited IPV resources should prioritize IPV use in routine immunization.
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Affiliation(s)
| | - Mark A. Pallansch
- Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Stephen L. Cochi
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Derek Ehrhardt
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Noha Farag
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Stephen Hadler
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Lee M. Hampton
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Maureen Martinez
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Steve G.F Wassilak
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
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Costa-Carvalho BT, Sullivan KE, Fontes PM, Aimé-Nobre F, Gonzales IGS, Lima ES, Granato C, de Moraes-Pinto MI. Low Rates of Poliovirus Antibodies in Primary Immunodeficiency Patients on Regular Intravenous Immunoglobulin Treatment. J Clin Immunol 2018; 38:628-634. [PMID: 30006913 DOI: 10.1007/s10875-018-0531-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 07/03/2018] [Indexed: 12/15/2022]
Abstract
PURPOSE Poliovirus has been nearly eliminated as part of a world-wide effort to immunize and contain circulating wild-type polio. Nevertheless, poliovirus has been detected in water supplies and represents a threat to patients with humoral immunodeficiencies where infection can be fatal. To define the risk, we analyzed antibodies to poliovirus 1, 2, and 3 in serum samples collected over a year from patients with primary immunodeficiency diseases (PID) on regular intravenous immunoglobulin (IVIG) replacement. METHODS Twenty-one patients on regular IVIG replacement therapy were evaluated: Twelve patients with common variable immune deficiency (CVID), six with X-linked agammaglobulinemia (XLA), and three with hyper IgM syndrome (HIGM). Over 1 year, four blood samples were collected from each of these patients immediately before immunoglobulin infusion. One sample of IVIG administered to each patient in the month before blood collection was also evaluated. Poliovirus antibodies were quantified by seroneutralization assay. RESULTS All IVIG samples had detectable antibodies to the three poliovirus serotypes. Despite that, only 52.4, 61.9, and 19.0% of patients showed protective antibody titers for poliovirus 1, 2, and 3, respectively. Only two patients (9.5%) had protective antibodies for the three poliovirus serotypes on all samples. Most patients were therefore susceptible to all three poliovirus serotypes. CONCLUSIONS This study demonstrates the need for ongoing vigilance regarding exposure of patients with PID to poliovirus in the community.
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Affiliation(s)
- Beatriz T Costa-Carvalho
- Division of Allergy Clinical Immunology and Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Kathleen E Sullivan
- Division of Allergy Immunology, The Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Patrícia M Fontes
- Division of Allergy Clinical Immunology and Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo, São Paulo, Brazil
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Fernanda Aimé-Nobre
- Division of Allergy Clinical Immunology and Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Isabela G S Gonzales
- Division of Allergy Clinical Immunology and Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Elaine S Lima
- Division of Infectious Diseases, Department of Medicine, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Celso Granato
- Division of Infectious Diseases, Department of Medicine, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Maria Isabel de Moraes-Pinto
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Universidade Federal de São Paulo, São Paulo, Brazil.
- Research Laboratory, Division of Pediatric Infectious Diseases, Federal University of Sao Paulo, Rua Pedro de Toledo, 781/9°andar, São Paulo, SP, 04039-032, Brazil.
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Kalkowska DA, Duintjer Tebbens RJ, Thompson KM. Another look at silent circulation of poliovirus in small populations. Infect Dis Model 2018; 3:107-117. [PMID: 30839913 PMCID: PMC6326228 DOI: 10.1016/j.idm.2018.06.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 04/13/2018] [Accepted: 06/01/2018] [Indexed: 11/26/2022] Open
Abstract
Background Silent circulation of polioviruses complicates the polio endgame and motivates analyses that explore the probability of undetected circulation for different scenarios. A recent analysis suggested a relatively high probability of unusually long silent circulation of polioviruses in small populations (defined as 10,000 people or smaller). Methods We independently replicated the simple, hypothetical model by Vallejo et al. (2017) and repeated their analyses to explore the model behavior, interpretation of the results, and implications of simplifying assumptions. Results We found a similar trend of increasing times between detected cases with increasing basic reproduction number (R0) and population size. However, we found substantially lower estimates of the probability of at least 3 years between successive polio cases than they reported, which appear more consistent with the prior literature. While small and isolated populations may sustain prolonged silent circulation, our reanalysis suggests that the existing rule of thumb of less than a 5% chance of 3 or more years of undetected circulation with perfect surveillance holds for most conditions of the model used by Vallejo et al. and most realistic conditions. Conclusions Avoiding gaps in surveillance remains critical to declaring wild poliovirus elimination with high confidence as soon as possible after the last detected poliovirus, but concern about transmission in small populations with adequate surveillance should not significantly change the criteria for the certification of wild polioviruses.
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Key Words
- AFP, acute flaccid paralysis
- CFP, case-free period
- CNC, confidence about no circulation
- CNCx%, time when the confidence about no circulation exceeds x%
- DEFP, detected-event-free period
- OPV, oral poliovirus vaccine
- POE, Probability of eradication
- Polio
- Silent circulation
- Small populations
- Stochastic modeling
- TBC, time between detected cases
- TUC, time of undetected circulation after the last detected-event
- TUCx%, xth percentile of the TUC
- WPV, wild poliovirus
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Affiliation(s)
| | | | - Kimberly M. Thompson
- Corresponding author. Kid Risk, Inc., 605 N. High St. #253, Columbus, OH 43215, USA.
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Tebbens RJD, Thompson KM. Using integrated modeling to support the global eradication of vaccine-preventable diseases. SYSTEM DYNAMICS REVIEW 2018; 34:78-120. [PMID: 34552305 PMCID: PMC8455164 DOI: 10.1002/sdr.1589] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 02/11/2018] [Indexed: 05/17/2023]
Abstract
The long-term management of global disease eradication initiatives involves numerous inherently dynamic processes, health and economic trade-offs, significant uncertainty and variability, rare events with big consequences, complex and inter-related decisions, and a requirement for cooperation among a large number of stakeholders. Over the course of more than 16 years of collaborative modeling efforts to support the Global Polio Eradication Initiative, we developed increasingly complex integrated system dynamics models that combined numerous analytical approaches, including differential equation-based modeling, risk and decision analysis, discrete-event and individual-based simulation, probabilistic uncertainty and sensitivity analysis, health economics, and optimization. We discuss the central role of systems thinking and system dynamics in the overall effort and the value of integrating different modeling approaches to appropriately address the trade-offs involved in some of the policy questions. We discuss practical challenges of integrating different analytical tools and we provide our perspective on the future of integrated modeling.
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Famulare M, Selinger C, McCarthy KA, Eckhoff PA, Chabot-Couture G. Assessing the stability of polio eradication after the withdrawal of oral polio vaccine. PLoS Biol 2018; 16:e2002468. [PMID: 29702638 PMCID: PMC5942853 DOI: 10.1371/journal.pbio.2002468] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 05/09/2018] [Accepted: 03/28/2018] [Indexed: 11/18/2022] Open
Abstract
The oral polio vaccine (OPV) contains live-attenuated polioviruses that induce immunity by causing low virulence infections in vaccine recipients and their close contacts. Widespread immunization with OPV has reduced the annual global burden of paralytic poliomyelitis by a factor of 10,000 or more and has driven wild poliovirus (WPV) to the brink of eradication. However, in instances that have so far been rare, OPV can paralyze vaccine recipients and generate vaccine-derived polio outbreaks. To complete polio eradication, OPV use should eventually cease, but doing so will leave a growing population fully susceptible to infection. If poliovirus is reintroduced after OPV cessation, under what conditions will OPV vaccination be required to interrupt transmission? Can conditions exist in which OPV and WPV reintroduction present similar risks of transmission? To answer these questions, we built a multi-scale mathematical model of infection and transmission calibrated to data from clinical trials and field epidemiology studies. At the within-host level, the model describes the effects of vaccination and waning immunity on shedding and oral susceptibility to infection. At the between-host level, the model emulates the interaction of shedding and oral susceptibility with sanitation and person-to-person contact patterns to determine the transmission rate in communities. Our results show that inactivated polio vaccine (IPV) is sufficient to prevent outbreaks in low transmission rate settings and that OPV can be reintroduced and withdrawn as needed in moderate transmission rate settings. However, in high transmission rate settings, the conditions that support vaccine-derived outbreaks have only been rare because population immunity has been high. Absent population immunity, the Sabin strains from OPV will be nearly as capable of causing outbreaks as WPV. If post-cessation outbreak responses are followed by new vaccine-derived outbreaks, strategies to restore population immunity will be required to ensure the stability of polio eradication. Oral polio vaccine (OPV) has played an essential role in the elimination of wild poliovirus (WPV). OPV contains attenuated (weakened) yet transmissible viruses that can spread from person to person. In its attenuated form, this spread is beneficial as it generates population immunity. However, the attenuation of OPV is unstable and it can, in rare instances, revert to a virulent form and cause vaccine-derived outbreaks of paralytic poliomyelitis. Thus, OPV is both a vaccine and a source of poliovirus, and for complete eradication, its use in vaccination must be ended. After OPV is no longer used in routine immunization, as with the cessation of type 2 OPV in 2016, population immunity to polioviruses will decline. A key question is how this loss of population immunity will affect the potential of OPV viruses to spread within and across communities. To address this, we examined the roles of immunity, sanitation, and social contact in limiting OPV transmission. Our results derive from an extensive review and synthesis of vaccine trial data and community epidemiological studies. Shedding, oral susceptibility to infection, and transmission data are analyzed to systematically explain and model observations of WPV and OPV circulation. We show that in high transmission rate settings, falling population immunity after OPV cessation will lead to conditions in which OPV and WPV are similarly capable of causing outbreaks, and that this conclusion is compatible with the known safety of OPV prior to global cessation. Novel strategies will be required to ensure the stability of polio eradication for all time.
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Affiliation(s)
- Michael Famulare
- Institute for Disease Modeling, Bellevue, Washington, United States of America
- * E-mail:
| | - Christian Selinger
- Institute for Disease Modeling, Bellevue, Washington, United States of America
| | - Kevin A. McCarthy
- Institute for Disease Modeling, Bellevue, Washington, United States of America
| | - Philip A. Eckhoff
- Institute for Disease Modeling, Bellevue, Washington, United States of America
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Duintjer Tebbens RJ, Hampton LM, Thompson KM. Planning for globally coordinated cessation of bivalent oral poliovirus vaccine: risks of non-synchronous cessation and unauthorized oral poliovirus vaccine use. BMC Infect Dis 2018; 18:165. [PMID: 29631539 PMCID: PMC5892013 DOI: 10.1186/s12879-018-3074-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 03/28/2018] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Oral polio vaccine (OPV) containing attenuated serotype 2 polioviruses was globally withdrawn in 2016, and bivalent OPV (bOPV) containing attenuated serotype 1 and 3 polioviruses needs to be withdrawn after the certification of eradication of all wild polioviruses to eliminate future risks from vaccine-derived polioviruses (VDPVs). To minimize risks from VDPVs, the planning and implementation of bOPV withdrawal should build on the experience with withdrawing OPV containing serotype 2 polioviruses while taking into account similarities and differences between the three poliovirus serotypes. METHODS We explored the risks from (i) a failure to synchronize OPV cessation and (ii) unauthorized post-cessation OPV use for serotypes 1 and 3 in the context of globally-coordinated future bOPV cessation and compared the results to similar analyses for serotype 2 OPV cessation. RESULTS While the risks associated with a failure to synchronize cessation and unauthorized post-cessation OPV use appear to be substantially lower for serotype 3 polioviruses than for serotype 2 polioviruses, the risks for serotype 1 appear similar to those for serotype 2. Increasing population immunity to serotype 1 and 3 poliovirus transmission using pre-cessation bOPV supplemental immunization activities and inactivated poliovirus vaccine in routine immunization reduces the risks of circulating VDPVs associated with non-synchronized cessation or unauthorized OPV use. CONCLUSIONS The Global Polio Eradication Initiative should synchronize global bOPV cessation during a similar window of time as occurred for the global cessation of OPV containing serotype 2 polioviruses and should rigorously verify the absence of bOPV in immunization systems after its cessation.
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Affiliation(s)
| | - Lee M. Hampton
- Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
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Abstract
To achieve complete polio eradication, the live oral poliovirus vaccine (OPV) currently used must be phased out after the end of wild poliovirus transmission. However, poorly understood threats may arise when OPV use is stopped. To counter these threats, better models than those currently available are needed. Two articles recently published in BMC Medicine address these issues. Mercer et al. (BMC Med 15:180, 2017) developed a statistical model analysis of polio case data and characteristics of cases occurring in several districts in Pakistan to inform resource allocation decisions. Nevertheless, despite having the potential to accelerate the elimination of polio cases, their analyses are unlikely to advance our understanding OPV cessation threats. McCarthy et al. (BMC Med 15:175, 2017) explored one such threat, namely the emergence and transmission of serotype 2 circulating vaccine derived poliovirus (cVDPV2) after OPV2 cessation, and found that the risk of persistent spread of cVDPV2 to new areas increases rapidly 1-5 years after OPV2 cessation. Thus, recently developed models and analysis methods have the potential to guide the required steps to surpass these threats. 'Big data' scientists could help with this; however, datasets covering all eradication efforts should be made readily available.Please see related articles: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0937-y and https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0941-2 .
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Affiliation(s)
- James S Koopman
- Deparment of Epidemiology, 1415 E. Washington Heights, Ann Arbor, MI, 48109, USA.
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Modelling Risk to US Military Populations from Stopping Blanket Mandatory Polio Vaccination. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2017; 2017:7981645. [PMID: 29104608 PMCID: PMC5618742 DOI: 10.1155/2017/7981645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 06/08/2017] [Indexed: 11/30/2022]
Abstract
Objectives Transmission of polio poses a threat to military forces when deploying to regions where such viruses are endemic. US-born soldiers generally enter service with immunity resulting from childhood immunization against polio; moreover, new recruits are routinely vaccinated with inactivated poliovirus vaccine (IPV), supplemented based upon deployment circumstances. Given residual protection from childhood vaccination, risk-based vaccination may sufficiently protect troops from polio transmission. Methods This analysis employed a mathematical system for polio transmission within military populations interacting with locals in a polio-endemic region to evaluate changes in vaccination policy. Results Removal of blanket immunization had no effect on simulated polio incidence among deployed military populations when risk-based immunization was employed; however, when these individuals reintegrated with their base populations, risk of transmission to nondeployed personnel increased by 19%. In the absence of both blanket- and risk-based immunization, transmission to nondeployed populations increased by 25%. The overall number of new infections among nondeployed populations was negligible for both scenarios due to high childhood immunization rates, partial protection against transmission conferred by IPV, and low global disease incidence levels. Conclusion Risk-based immunization driven by deployment to polio-endemic regions is sufficient to prevent transmission among both deployed and nondeployed US military populations.
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Vallejo C, Keesling J, Koopman J, Singer B. Silent circulation of poliovirus in small populations. Infect Dis Model 2017; 2:431-440. [PMID: 30137721 PMCID: PMC6001964 DOI: 10.1016/j.idm.2017.11.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 10/06/2017] [Accepted: 11/02/2017] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Small populations that have been isolated by conflict make vaccination and surveillance difficult, threatening polio eradication. Silent circulation is caused by asymptomatic infections. It is currently not clear whether the dynamics of waning immunity also influence the risk of silent circulation in the absence of vaccination. Such circulation can, nevertheless, be present following a declaration of elimination as a result of inadequate acute flaccid paralysis surveillance (AFPS) or environmental surveillance (ES). METHODS We have constructed a stochastic model to understand how stochastic effects alter the ability of small populations to sustain virus circulation in the absence of vaccination. We analyzed how the stochastic process determinants of the duration of silent circulation that could have been detected by ES were affected by R 0 , waning dynamics, population size, and AFPS sensitivity in a discrete individual stochastic model with homogeneous contagiousness and random mixing. We measured the duration of silent circulation both by the interval between detected acute flaccid paralysis (AFP) cases and the duration of circulation until elimination. RESULTS As R 0 increased and population size increased, the interval between detected AFP cases and the duration of circulation until elimination increased. As AFPS detection rates decreased, the interval between detected AFP cases increased. There was up to a 22 % chance of silent circulation lasting for more than 3 years with 100 % AFP detection. The duration of silent circulation was not affected by the waning immunity dynamics. CONCLUSION We demonstrated that small populations have the potential to sustain prolonged silent circulation. Surveillance in these areas should be intensified before declaring elimination. To further validate these conclusions, it is necessary to realistically relax the simplifying assumptions about mixing and waning.
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Affiliation(s)
- Celeste Vallejo
- Department of Mathematics, 1400 Stadium Rd, University of Florida, Gainesville, FL 32611, United States
| | - James Keesling
- Department of Mathematics, 1400 Stadium Rd, University of Florida, Gainesville, FL 32611, United States
| | - James Koopman
- School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109-2029, United States
| | - Burton Singer
- Emerging Pathogens Institute, University of Florida, P.O. Box 100009, 2055 Mowry Road, Gainesville, FL 32610, United States
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Abstract
BACKGROUND Wild type 2 poliovirus was last observed in 1999. The Sabin-strain oral polio vaccine type 2 (OPV2) was critical to eradication, but it is known to revert to a neurovirulent phenotype, causing vaccine-associated paralytic poliomyelitis. OPV2 is also transmissible and can establish circulating lineages, called circulating vaccine-derived polioviruses (cVDPVs), which can also cause paralytic outbreaks. Thus, in April 2016, OPV2 was removed from immunization activities worldwide. Interrupting transmission of cVDPV2 lineages that survive cessation will require OPV2 in outbreak response, which risks seeding new cVDPVs. This potential cascade of outbreak responses seeding VDPVs, necessitating further outbreak responses, presents a critical risk to the OPV2 cessation effort. METHODS The EMOD individual-based disease transmission model was used to investigate OPV2 use in outbreak response post-cessation in West African populations. A hypothetical outbreak response in northwest Nigeria is modeled, and a cVDPV2 lineage is considered established if the Sabin strain escapes the response region and continues circulating 9 months post-response. The probability of this event was investigated in a variety of possible scenarios. RESULTS Under a broad range of scenarios, the probability that widespread OPV2 use in outbreak response (~2 million doses) establishes new cVDPV2 lineages in this model may exceed 50% as soon as 18 months or as late as 4 years post-cessation. CONCLUSIONS The risk of a cycle in which outbreak responses seed new cVDPV2 lineages suggests that OPV2 use should be managed carefully as time from cessation increases. It is unclear whether this risk can be mitigated in the long term, as mucosal immunity against type 2 poliovirus declines globally. Therefore, current programmatic strategies should aim to minimize the possibility that continued OPV2 use will be necessary in future years: conducting rapid and aggressive outbreak responses where cVDPV2 lineages are discovered, maintaining high-quality surveillance in all high-risk settings, strengthening the use of the inactivated polio vaccine as a booster in the OPV2-exposed and in routine immunization, and gaining access to currently inaccessible areas of the world to conduct surveillance.
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Thompson KM, Duintjer Tebbens RJ. Lessons From Globally Coordinated Cessation of Serotype 2 Oral Poliovirus Vaccine for the Remaining Serotypes. J Infect Dis 2017; 216:S168-S175. [PMID: 28838198 PMCID: PMC5853947 DOI: 10.1093/infdis/jix128] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/06/2017] [Accepted: 03/13/2017] [Indexed: 12/12/2022] Open
Abstract
Background Comparing model expectations with the experience of oral poliovirus vaccine (OPV) containing serotype 2 (OPV2) cessation can inform risk management for the expected cessation of OPV containing serotypes 1 and 3 (OPV13). Methods We compare the expected post-OPV2-cessation OPV2-related viruses from models with the evidence available approximately 6 months after OPV2 cessation. We also model the trade-offs of use vs nonuse of monovalent OPV (mOPV) for outbreak response considering all 3 serotypes. Results Although too early to tell definitively, the observed die-out of OPV2-related viruses in populations that attained sufficiently intense trivalent OPV (tOPV) use prior to OPV2 cessation appears consistent with model expectations. As expected, populations that did not intensify tOPV use prior to OPV2 cessation show continued circulation of serotype 2 vaccine-derived polioviruses (VDPVs). Failure to aggressively use mOPV to respond to circulating VDPVs results in a high risk of uncontrolled outbreaks that would require restarting OPV. Conclusions Ensuring a successful endgame requires more aggressive OPV cessation risk management than has occurred to date for OPV2 cessation. This includes maintaining high population immunity to transmission up until OPV13 cessation, meeting all prerequisites for OPV cessation, and ensuring sufficient vaccine supply to prevent and respond to outbreaks.
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Thompson KM, Duintjer Tebbens RJ. Lessons From the Polio Endgame: Overcoming the Failure to Vaccinate and the Role of Subpopulations in Maintaining Transmission. J Infect Dis 2017; 216:S176-S182. [PMID: 28838194 PMCID: PMC5853387 DOI: 10.1093/infdis/jix108] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Background Recent detections of circulating serotype 2 vaccine-derived poliovirus in northern Nigeria (Borno and Sokoto states) and Pakistan (Balochistan Province) and serotype 1 wild poliovirus in Pakistan, Afghanistan, and Nigeria (Borno) represent public health emergencies that require aggressive response. Methods We demonstrate the importance of undervaccinated subpopulations, using an existing dynamic poliovirus transmission and oral poliovirus vaccine evolution model. We review the lessons learned during the polio endgame about the role of subpopulations in sustaining transmission, and we explore the implications of subpopulations for other vaccine-preventable disease eradication efforts. Results Relatively isolated subpopulations benefit little from high surrounding population immunity to transmission and will sustain transmission as long as they do not attain high vaccination coverage. Failing to reach such subpopulations with high coverage represents the root cause of polio eradication delays. Achieving and maintaining eradication requires addressing the weakest links, which includes immunizing populations in insecure areas and/or with disrupted or poor-performing health systems and managing the risks of individuals with primary immunodeficiencies who can excrete vaccine-derived poliovirus long-term. Conclusions Eradication efforts for vaccine-preventable diseases need to create performance expectations for countries to immunize all people living within their borders and maintain high coverage with appropriate interventions.Keywords. Polio; eradication; transmission; heterogeneity.
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Thompson KM, Badizadegan ND. Modeling the Transmission of Measles and Rubella to Support Global Management Policy Analyses and Eradication Investment Cases. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2017; 37:1109-1131. [PMID: 28561947 DOI: 10.1111/risa.12831] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 04/03/2017] [Accepted: 04/06/2017] [Indexed: 06/07/2023]
Abstract
Policy makers responsible for managing measles and rubella immunization programs currently use a wide range of different vaccines formulations and immunization schedules. With endemic measles and rubella transmission interrupted in the region of the Americas, all five other regions of the World Health Organization (WHO) targeting the elimination of measles transmission by 2020, and increasing adoption of rubella vaccine globally, integrated dynamic disease, risk, decision, and economic models can help national, regional, and global health leaders manage measles and rubella population immunity. Despite hundreds of publications describing models for measles or rubella and decades of use of vaccines that contain both antigens (e.g., measles, mumps, and rubella vaccine or MMR), no transmission models for measles and rubella exist to support global policy analyses. We describe the development of a dynamic disease model for measles and rubella transmission, which we apply to 180 WHO member states and three other areas (Puerto Rico, Hong Kong, and Macao) representing >99.5% of the global population in 2013. The model accounts for seasonality, age-heterogeneous mixing, and the potential existence of preferentially mixing undervaccinated subpopulations, which create heterogeneity in immunization coverage that impacts transmission. Using our transmission model with the best available information about routine, supplemental, and outbreak response immunization, we characterize the complex transmission dynamics for measles and rubella historically to compare the results with available incidence and serological data. We show the results from several countries that represent diverse epidemiological situations to demonstrate the performance of the model. The model suggests relatively high measles and rubella control costs of approximately $3 billion annually for vaccination based on 2013 estimates, but still leads to approximately 17 million disability-adjusted life years lost with associated costs for treatment, home care, and productivity loss costs of approximately $4, $3, and $47 billion annually, respectively. Combined with vaccination and other financial cost estimates, our estimates imply that the eradication of measles and rubella could save at least $10 billion per year, even without considering the benefits of preventing lost productivity and potential savings from reductions in vaccination. The model should provide a useful tool for exploring the health and economic outcomes of prospective opportunities to manage measles and rubella. Improving the quality of data available to support decision making and modeling should represent a priority as countries work toward measles and rubella goals.
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Affiliation(s)
- Kimberly M Thompson
- Kid Risk, Inc., Orlando, FL, USA
- University of Central Florida College of Medicine, Orlando, FL, USA
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Duintjer Tebbens RJ, Thompson KM. Poliovirus vaccination during the endgame: insights from integrated modeling. Expert Rev Vaccines 2017; 16:577-586. [DOI: 10.1080/14760584.2017.1322514] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
| | - Kimberly M. Thompson
- Kid Risk, Inc., Orlando, FL, USA
- College of Medicine, University of Central Florida, Orlando, FL, USA
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Koopman JS, Henry CJ, Park JH, Eisenberg MC, Ionides EL, Eisenberg JN. Dynamics affecting the risk of silent circulation when oral polio vaccination is stopped. Epidemics 2017; 20:21-36. [PMID: 28283373 PMCID: PMC5608688 DOI: 10.1016/j.epidem.2017.02.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 02/20/2017] [Accepted: 02/20/2017] [Indexed: 12/15/2022] Open
Abstract
Silent circulation (SC) of wild polio viruses (WPV) when oral polio vaccine (OPV) use is stopped, could threaten eradication. We analyzed a model designed to develop theory about mechanisms and factors that lead to SC and how SC risks can be assessed using surveillance data. Prolonged low-level SC emerges as a threshold phenomenon through a mechanism related to balancing contributions of different populations to the effective reproduction number. Factors that promote this mechanism are many years of inadequate vaccination efforts, ongoing waning of immunity against transmission years after last OPV or WPV infection, low transmissibility of OPV, and high transmission conditions. Analyzing acute flaccid paralysis surveillance or environmental surveillance data by themselves cannot assess the risk that an SC threshold has been passed, but new methods to analyze them jointly could do so.
Waning immunity could allow transmission of polioviruses without causing poliomyelitis by promoting silent circulation (SC). Undetected SC when oral polio vaccine (OPV) use is stopped could cause difficult to control epidemics. Little is known about waning. To develop theory about what generates SC, we modeled a range of waning patterns. We varied both OPV and wild polio virus (WPV) transmissibility, the time from beginning vaccination to reaching low polio levels, and the infection to paralysis ratio (IPR). There was longer SC when waning continued over time rather than stopping after a few years, when WPV transmissibility was higher or OPV transmissibility was lower, and when the IPR was higher. These interacted in a way that makes recent emergence of prolonged SC a possibility. As the time to reach low infection levels increased, vaccine rates needed to eliminate polio increased and a threshold was passed where prolonged low-level SC emerged. These phenomena were caused by increased contributions to the force of infection from reinfections. The resulting SC occurs at low levels that would be difficult to detect using environmental surveillance. For all waning patterns, modest levels of vaccination of adults shortened SC. Previous modeling studies may have missed these phenomena because (1) they used models with no or very short duration waning and (2) they fit models to paralytic polio case counts. Our analyses show that polio case counts cannot predict SC because nearly identical polio case count patterns can be generated by a range of waning patterns that generate different patterns of SC. We conclude that the possibility of prolonged SC is real but unquantified, that vaccinating modest fractions of adults could reduce SC risk, and that joint analysis of acute flaccid paralysis and environmental surveillance data can help assess SC risks and ensure low risks before stopping OPV.
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Affiliation(s)
- J S Koopman
- Department of Epidemiology, University of Michigan School of Public Health, United States.
| | - C J Henry
- Department of Epidemiology, University of Michigan School of Public Health, United States
| | - J H Park
- Department of Statistics, University of Michigan School of Literature, Science, and the Arts, United States
| | - M C Eisenberg
- Department of Epidemiology, University of Michigan School of Public Health, United States
| | - E L Ionides
- Department of Statistics, University of Michigan School of Literature, Science, and the Arts, United States
| | - J N Eisenberg
- Department of Epidemiology, University of Michigan School of Public Health, United States
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Duintjer Tebbens RJ, Thompson KM. Costs and Benefits of Including Inactivated in Addition to Oral Poliovirus Vaccine in Outbreak Response After Cessation of Oral Poliovirus Vaccine Use. MDM Policy Pract 2017; 2:2381468317697002. [PMID: 30288417 PMCID: PMC6124926 DOI: 10.1177/2381468317697002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 12/02/2016] [Indexed: 01/24/2023] Open
Abstract
Background: After stopping serotype 2-containing oral poliovirus vaccine use, serotype 2 poliovirus outbreaks may still occur and require outbreak response supplemental immunization activities (oSIAs). Current oSIA plans include the use of both serotype 2 monovalent oral poliovirus vaccine (mOPV2) and inactivated poliovirus vaccine (IPV). Methods: We used an existing model to compare the effectiveness of mOPV2 oSIAs with or without IPV in response to a hypothetical postcessation serotype 2 outbreak in northwest Nigeria. We considered strategies that co-administer IPV with mOPV2, use IPV only for older age groups, or use only IPV during at least one oSIA. We considered the cost and supply implications and estimated from a societal perspective the incremental cost-effectiveness and incremental net benefits of adding IPV to oSIAs in the context of this hypothetical outbreak in 2017. Results: Adding IPV to the first or second oSIA resulted in a 4% to 6% reduction in expected polio cases compared to exclusive mOPV2 oSIAs. We found the greatest benefit of IPV use if added preemptively as a ring around the initial oSIA target population, and negligible benefit if added to later oSIAs or older age groups. We saw an increase in expected polio cases if IPV replaced mOPV2 during an oSIA. None of the oSIA strategies that included IPV for this outbreak represented a cost-effective or net beneficial intervention compared to reliance on mOPV2 only. Conclusions: While adding IPV to oSIAs results in marginal improvements in performance, the poor cost-effectiveness and current limited IPV supply make it economically unattractive for high-risk settings in which IPV does not significantly affect transmission.
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Duintjer Tebbens RJ, Thompson KM. The potential benefits of a new poliovirus vaccine for long-term poliovirus risk management. Future Microbiol 2016; 11:1549-1561. [DOI: 10.2217/fmb-2016-0126] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Aim: To estimate the incremental net benefits (INBs) of a hypothetical ideal vaccine with all of the advantages and no disadvantages of existing oral and inactivated poliovirus vaccines compared with current vaccines available for future outbreak response. Methods: INB estimates based on expected costs and polio cases from an existing global model of long-term poliovirus risk management. Results: Excluding the development costs, an ideal poliovirus vaccine could offer expected INBs of US$1.6 billion. The ideal vaccine yields small benefits in most realizations of long-term risks, but great benefits in low-probability–high-consequence realizations. Conclusion: New poliovirus vaccines may offer valuable insurance against long-term poliovirus risks and new vaccine development efforts should continue as the world gathers more evidence about polio endgame risks.
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Comprehensive screening for immunodeficiency-associated vaccine-derived poliovirus: an essential oral poliovirus vaccine cessation risk management strategy. Epidemiol Infect 2016; 145:217-226. [PMID: 27760579 PMCID: PMC5197684 DOI: 10.1017/s0950268816002302] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
If the world can successfully control all outbreaks of circulating vaccine-derived poliovirus that may occur soon after global oral poliovirus vaccine (OPV) cessation, then immunodeficiency-associated vaccine-derived polioviruses (iVDPVs) from rare and mostly asymptomatic long-term excretors (defined as ⩾6 months of excretion) will become the main source of potential poliovirus outbreaks for as long as iVDPV excretion continues. Using existing models of global iVDPV prevalence and global long-term poliovirus risk management, we explore the implications of uncertainties related to iVDPV risks, including the ability to identify asymptomatic iVDPV excretors to treat with polio antiviral drugs (PAVDs) and the transmissibility of iVDPVs. The expected benefits of expanded screening to identify and treat long-term iVDPV excretors with PAVDs range from US$0.7 to 1.5 billion with the identification of 25–90% of asymptomatic long-term iVDPV excretors, respectively. However, these estimates depend strongly on assumptions about the transmissibility of iVDPVs and model inputs affecting the global iVDPV prevalence. For example, the expected benefits may decrease to as low as US$260 million with the identification of 90% of asymptomatic iVDPV excretors if iVDPVs behave and transmit like partially reverted viruses instead of fully reverted viruses. Comprehensive screening for iVDPVs will reduce uncertainties and maximize the expected benefits of PAVD use.
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