1
|
Martin LB, Khanam F, Qadri F, Khalil I, Sikorski MJ, Baker S. Vaccine value profile for Salmonella enterica serovar Paratyphi A. Vaccine 2023; 41 Suppl 2:S114-S133. [PMID: 37951691 DOI: 10.1016/j.vaccine.2023.01.054] [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: 10/02/2022] [Revised: 12/27/2022] [Accepted: 01/23/2023] [Indexed: 11/14/2023]
Abstract
In Asia, there are an estimated 12 million annual cases of enteric fever, a potentially fatal systemic bacterial infection caused by Salmonella enterica serovars Typhi (STy) and Paratyphi A (SPA). The recent availability of typhoid conjugate vaccines (TCV), an increasing incidence of disease caused by SPA and growing antimicrobial resistance (AMR) across the genus Salmonella makes a bivalent STy/SPA vaccine a useful public health proposition. The uptake of a stand-alone paratyphoid vaccine is likely low thus, there is a pipeline of bivalent STy/SPA candidate vaccines. Several candidates are close to entering clinical trials, which if successful should facilitate a more comprehensive approach for enteric fever control. Additionally, the World Health Organization (WHO) has made advancing the development of vaccines that protect young children and working aged adults against both agents of enteric fever a priority objective. This "Vaccine Value Profile" (VVP) addresses information related predominantly to invasive disease caused by SPA prevalent in Asia. Information is included on stand-alone SPA candidate vaccines and candidate vaccines targeting SPA combined with STy. Out of scope for the first version of this VVP is a wider discussion on the development of a universal Salmonella combination candidate vaccine, addressing both enteric fever and invasive non-typhoidal Salmonella disease, for use globally. This VVP is a detailed, high-level assessment of existing, publicly available information to inform and contextualize the public health, economic, and societal potential of pipeline vaccines and vaccine-like products for SPA. Future versions of this VVP will be updated to reflect ongoing activities such as vaccine development strategies and "Full Vaccine Value Assessment" that will inform the value proposition of an SPA vaccine. This VVP was developed by an expert working group from academia, non-profit organizations, public-private partnerships, and multi-lateral organizations as well as in collaboration with stakeholders from the WHO South-East Asian Region. All contributors have extensive expertise on various elements of the VVP for SPA and collectively aimed to identify current research and knowledge gaps.
Collapse
Affiliation(s)
- Laura B Martin
- Independent Consultant (current affiliation US Pharmacopeia Convention), USA.
| | - Farhana Khanam
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Bangladesh.
| | - Firdausi Qadri
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Bangladesh.
| | | | | | - Stephen Baker
- University of Cambridge School of Clinical Medicine, UK.
| |
Collapse
|
2
|
Mathematical Models for Typhoid Disease Transmission: A Systematic Literature Review. MATHEMATICS 2022. [DOI: 10.3390/math10142506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Explaining all published articles on the typhoid disease transmission model was carried out. It has been conducted to understand how Salmonella is transmitted among humans and vectors with variation interventions to control the spread of the typhoid disease. Specific objectives were to (1) identify the model developed, (2) describe the studies, and (3) identify the interventions of the model. It systemically searched and reviewed Dimension, Scopus, and ScienceDirect databases from 2013 through to 2022 for articles that studied the spread of typhoid fever through a compartmental mathematical model. This study obtained 111 unique articles from three databases, resulting in 23 articles corresponding to the created terms. All the articles were elaborated on to identify their identities for more explanation. Various interventions were considered in the model of each article, are identified, and then summarized to find out the opportunities for model development in future works. The whole article’s content was identified and outlined regarding how mathematics plays a role in model analysis and study of typhoid disease spread with various interventions. The study of mathematical modeling for typhoid disease transmission can be developed on analysis and creating the model with direct and indirect interventions to the human population for further work.
Collapse
|
3
|
Birger R, Antillón M, Bilcke J, Dolecek C, Dougan G, Pollard AJ, Neuzil KM, Frost I, Laxminarayan R, Pitzer VE. Estimating the effect of vaccination on antimicrobial-resistant typhoid fever in 73 countries supported by Gavi: a mathematical modelling study. THE LANCET INFECTIOUS DISEASES 2022; 22:679-691. [PMID: 35123673 PMCID: PMC9021026 DOI: 10.1016/s1473-3099(21)00627-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 08/20/2021] [Accepted: 09/23/2021] [Indexed: 11/24/2022]
|
4
|
Qu Z, McMahon BH, Perkins DJ, Hyman JM. Staged progression epidemic models for the transmission of invasive nontyphoidal Salmonella (iNTS) with treatment. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2021; 18:1529-1549. [PMID: 33757197 PMCID: PMC11064643 DOI: 10.3934/mbe.2021079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We develop and analyze a stage-progression compartmental model to study the emerging invasive nontyphoidal Salmonella (iNTS) epidemic in sub-Saharan Africa. iNTS bloodstream infections are often fatal, and the diverse and non-specific clinical features of iNTS make it difficult to diagnose. We focus our study on identifying approaches that can reduce the incidence of new infections. In sub-Saharan Africa, transmission and mortality are correlated with the ongoing HIV epidemic and severe malnutrition. We use our model to quantify the impact that increasing antiretroviral therapy (ART) for HIV infected adults and reducing malnutrition in children would have on mortality from iNTS in the population. We consider immunocompromised subpopulations in the region with major risk factors for mortality, such as malaria and malnutrition among children and HIV infection and ART coverage in both children and adults. We parameterize the progression rates between infection stages using the branching probabilities and estimated time spent at each stage. We interpret the basic reproduction number R0 as the total contribution from an infinite infection loop produced by the asymptomatic carriers in the infection chain. The results indicate that the asymptomatic HIV+ adults without ART serve as the driving force of infection for the iNTS epidemic. We conclude that the worst disease outcome is among the pediatric population, which has the highest infection rates and death counts. Our sensitivity analysis indicates that the most effective strategies to reduce iNTS mortality in the studied population are to improve the ART coverage among high-risk HIV+ adults and reduce malnutrition among children.
Collapse
Affiliation(s)
- Zhuolin Qu
- Department of Mathematics, University of Texas at San Antonio, San Antonio 78202, TX, USA
| | - Benjamin H. McMahon
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Douglas J. Perkins
- University of New Mexico, Center for Global Health, Department of Internal Medicine, NM, USA
- University of New Mexico-Kenya Global Health Programs, Kisumu and Siaya, Kenya
| | - James M. Hyman
- Department of Mathematics, Tulane University, New Orleans 70112, LA, USA
| |
Collapse
|
5
|
Acosta-Alonzo CB, Erovenko IV, Lancaster A, Oh H, Rychtář J, Taylor D. High endemic levels of typhoid fever in rural areas of Ghana may stem from optimal voluntary vaccination behaviour. Proc Math Phys Eng Sci 2020; 476:20200354. [PMID: 33071586 DOI: 10.1098/rspa.2020.0354] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 08/04/2020] [Indexed: 01/24/2023] Open
Abstract
Typhoid fever has long established itself endemically in rural Ghana despite the availability of cheap and effective vaccines. We used a game-theoretic model to investigate whether the low vaccination coverage in Ghana could be attributed to rational human behaviour. We adopted a version of an epidemiological model of typhoid fever dynamics, which accounted not only for chronic life-long carriers but also for a short-cycle transmission in the immediate environment and a long-cycle transmission via contamination of the water supply. We calibrated the model parameters based on the known incidence data. We found that unless the (perceived) cost of vaccination is negligible, the individually optimal population vaccination rate falls significantly short of the societally optimal population vaccination rate needed to reach herd immunity. We expressed both the herd immunity and the optimal equilibrium vaccination rates in terms of only a few observable parameters such as the incidence rate, demographics, vaccine waning rate and the perceived cost of vaccination relative to the cost of infection. This allowed us not to rely on other uncertain epidemiological model parameters and, in particular, to bypass uncertainties about the role of the carriers in the transmission.
Collapse
Affiliation(s)
- Carmen B Acosta-Alonzo
- Department of Mathematics and Computer Science, Bennett College, Greensboro, NC 27401, USA
| | - Igor V Erovenko
- Department of Mathematics and Statistics, University of North Carolina at Greensboro, Greensboro, NC 27402, USA
| | - Aaleah Lancaster
- Department of Mathematics and Computer Science, Bennett College, Greensboro, NC 27401, USA
| | - Hyunju Oh
- Division of Mathematics and Computer Science, University of Guam, Mangilao, Guam 96923, 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
| |
Collapse
|
6
|
Gibani MM, Voysey M, Jin C, Jones C, Thomaides-Brears H, Jones E, Baker P, Morgan M, Simmons A, Gordon MA, Cerundolo V, Pitzer VE, Angus B, Levine MM, Darton TC, Pollard AJ. The Impact of Vaccination and Prior Exposure on Stool Shedding of Salmonella Typhi and Salmonella Paratyphi in 6 Controlled Human Infection Studies. Clin Infect Dis 2020; 68:1265-1273. [PMID: 30252031 PMCID: PMC6452003 DOI: 10.1093/cid/ciy670] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 08/07/2018] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Shedding of Salmonella Typhi or Paratyphi in the stool or urine leads to contamination of food or water, which is a prerequisite for transmission of enteric fever. Currently, there are limited data on the effect of vaccination or prior exposure on stool shedding. METHODS Six Salmonella Typhi or Paratyphi human challenge studies were conducted between 2011 and 2017. Participants were either unvaccinated or vaccinated with 1 of 4 vaccines: Vi-polysaccharide (Vi-PS), Vi-tetanus-toxoid conjugate vaccine (Vi-TT), live oral Ty21a vaccine, or an experimental vaccine (M01ZH09). Daily stool cultures were collected for 14 days after challenge. RESULTS There were 4934 stool samples collected from 430 volunteers. Participants who received Vi-PS or Vi-TT shed less than unvaccinated participants (odds ratio [OR], 0.34; 95% confidence interval [CI], 0.15-0.77; P = .010 and OR, 0.41; 95% CI, 0.19-0.91, P = .029 for Vi-PS and Vi-TT, respectively). Higher anti-Vi immunoglobulin G titers were associated with less shedding of S. Typhi (P < .0001). A nonsignificant reduction in shedding was associated with Ty21a vaccine (OR, 0.57; 95% CI, 0.27-1.20; P = .140). Individuals previously exposed to S. Typhi shed less than previously unexposed individuals (OR, 0.30; 95% CI, 0.1-0.8; P = .016). Shedding of S. Typhi was more common than S. Paratyphi. CONCLUSIONS Prior vaccination with Vi vaccines, or natural infection, reduces onward transmission of S. Typhi. Field trials of Vi-TT should be designed to detect indirect protection, reflecting the consequence of reduced stool shedding observed in the human challenge model.
Collapse
Affiliation(s)
- Malick M Gibani
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford
| | - Merryn Voysey
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford.,Nuffield Department of Primary Care Health Sciences, University of Oxford, United Kingdom
| | - Celina Jin
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford
| | - Claire Jones
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford
| | | | - Elizabeth Jones
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford
| | - Philip Baker
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford
| | - Marcus Morgan
- Oxford University Hospitals, National Health Service Foundation Trust, United Kingdom
| | - Alison Simmons
- Medical Research Council Human Immunology Unit, Radcliffe Department of Medicine, University of Oxford, United Kingdom.,Translational Gastroenterology Unit, University of Oxford, United Kingdom
| | - Melita A Gordon
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre.,Institute for Infection and Global Health, University of Liverpool, United Kingdom
| | - Vincenzo Cerundolo
- Medical Research Council Human Immunology Unit, Radcliffe Department of Medicine, University of Oxford, United Kingdom
| | - Virginia E Pitzer
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut
| | - Brian Angus
- Oxford University Hospitals, National Health Service Foundation Trust, United Kingdom.,Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Myron M Levine
- Center for Vaccine Development, University of Maryland School of Medicine, Baltimore
| | - Thomas C Darton
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford.,Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield
| | - Andrew J Pollard
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford.,National Institute for Health Research Oxford Biomedical Research Centre, United Kingdom
| |
Collapse
|
7
|
Frempong SN, Sutton AJ, Davenport C, Barton P. Early Economic Evaluation to Identify the Necessary Test Characteristics of a New Typhoid Test to be Cost Effective in Ghana. PHARMACOECONOMICS - OPEN 2020; 4:143-157. [PMID: 31377968 PMCID: PMC7018929 DOI: 10.1007/s41669-019-0159-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
BACKGROUND In Ghana, there are issues with the diagnosis of typhoid fever; these include delays in diagnosis, concerns about the accuracy of current tests, and lack of availability. These issues highlight the need for the development of a rapid, accurate, and easily accessible diagnostic test. The aim of this study was to conduct an early economic analysis of a hypothetical rapid test for typhoid fever diagnosis in Ghana and identify the necessary characteristics of the test for it to be cost effective in Ghana. METHODS An early cost-utility analysis was conducted using a decision tree parameterized with secondary data sources, with reasonable assumptions made for unknown parameters. The patient population considered is individuals presenting with symptoms suggestive of typhoid fever at a healthcare facility in Ghana; a time horizon of 180 days and the Ghanaian national health service perspective were adopted for the analysis. Extensive sensitivity analysis was undertaken, including headroom analysis. RESULTS The results here show that for a hypothetical test to perform better than the existing test (Widal) in terms of QALYs gained and cost effectiveness, it is necessary for it to have a high specificity (at least 70%) and should not be priced more than US$4. The overall value of conducting research to reduce uncertainty (over 5 years) is US$3287. CONCLUSION The analysis shows the potential for the hypothetical test to replace the Widal test and the market potential of developing a new test in the Ghanaian setting.
Collapse
Affiliation(s)
- Samuel N Frempong
- Institute of Applied Health Research, University of Birmingham, Birmingham, UK
| | - Andrew J Sutton
- Institute of Health Economics, 1200 10405 Jasper Avenue, Edmonton, AB, T5J 3N4, Canada.
| | - Clare Davenport
- Institute of Applied Health Research, University of Birmingham, Birmingham, UK
| | - Pelham Barton
- Institute of Applied Health Research, University of Birmingham, Birmingham, UK
| |
Collapse
|
8
|
Marchello CS, Dale AP, Pisharody S, Crump JA. Using hospital-based studies of community-onset bloodstream infections to make inferences about typhoid fever incidence. Trop Med Int Health 2019; 24:1369-1383. [PMID: 31633858 PMCID: PMC6916262 DOI: 10.1111/tmi.13319] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Objectives Hospital-based studies of community-onset bloodstream infections (CO-BSI) are less resource-intensive to carry out than population-based incidence studies. We examined several metrics capturing the potential role of Salmonella Typhi as a cause of CO-BSI for making inferences about incidence. Methods We systematically reviewed three databases for hospital-based studies of CO-BSI. We determined, by study, the prevalence and rank order of Salmonella among pathogenic bloodstream isolates, and the prevalence ratio of Salmonella Typhi to Escherichia coli (S:E ratio). We then describe these hospital-based study metrics in relation to population-based typhoid fever incidence data from a separate systematic review. Results Forty-four studies met the inclusion criteria, of which 23 (52.3%) isolated Salmonella Typhi at least once. Among studies isolating Salmonella Typhi, the median (interquartile range) prevalence and rank order of Salmonella Typhi compared to other pathogens isolated in BSI was 8.3% (3.2–37.9%) and 3 (1–6), respectively. The median (interquartile range) S:E ratio was 1.0 (0.4–3.0). With respect to incidence, in Pemba Island, Tanzania, prevalence, rank order, S:E ratio, and incidence was 64.8%, 1, 9.2 and 110 cases per 100 000, respectively, and in Boulkiemdé, Burkina Faso, was 13.3%, 3, 2.3 and 249 cases per 100 000. Conclusions We describe considerable variation in place and time for Salmonella Typhi prevalence, rank order, and S:E ratio among hospital-based studies of CO-BSI. Data from simultaneous typhoid prevalence and incidence studies are limited. We propose that hospital-based study metrics warrant evaluation for making inference about typhoid incidence and as covariates in typhoid incidence models.
Collapse
Affiliation(s)
| | - Ariella P Dale
- Colorado Department of Public Health and Environment, Denver, CO, USA
| | | | - John A Crump
- Centre for International Health, University of Otago, Dunedin, New Zealand
| |
Collapse
|
9
|
Lo NC, Gupta R, Stanaway JD, Garrett DO, Bogoch II, Luby SP, Andrews JR. Comparison of Strategies and Incidence Thresholds for Vi Conjugate Vaccines Against Typhoid Fever: A Cost-effectiveness Modeling Study. J Infect Dis 2019; 218:S232-S242. [PMID: 29444257 PMCID: PMC6226717 DOI: 10.1093/infdis/jix598] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Background Typhoid fever remains a major public health problem globally. While new Vi conjugate vaccines hold promise for averting disease, the optimal programmatic delivery remains unclear. We aimed to identify the strategies and associated epidemiologic conditions under which Vi conjugate vaccines would be cost-effective. Methods We developed a dynamic, age-structured transmission and cost-effectiveness model that simulated multiple vaccination strategies with a typhoid Vi conjugate vaccine from a societal perspective. We simulated 10-year vaccination programs with (1) routine immunization of infants (aged <1 year) through the Expanded Program on Immunization (EPI) and (2) routine immunization of infants through the EPI plus a 1-time catch-up campaign in school-aged children (aged 5–14 years). In the base case analysis, we assumed a 0.5% case-fatality rate for all cases of clinically symptomatic typhoid fever and defined strategies as highly cost-effective by using the definition of a low-income country (defined as a country with a gross domestic product of $1045 per capita). We defined incidence as the true number of clinically symptomatic people in the population per year. Results Vi conjugate typhoid vaccines were highly cost-effective when administered by routine immunization activities through the EPI in settings with an annual incidence of >50 cases/100000 (95% uncertainty interval, 40–75 cases) and when administered through the EPI plus a catch-up campaign in settings with an annual incidence of >130 cases/100000 (95% uncertainty interval, 50–395 cases). The incidence threshold was sensitive to the typhoid-related case-fatality rate, carrier contribution to transmission, vaccine characteristics, and country-specific economic threshold for cost-effectiveness. Conclusions Typhoid Vi conjugate vaccines would be highly cost-effective in low-income countries in settings of moderate typhoid incidence (50 cases/100000 annually). These results were sensitive to case-fatality rates, underscoring the need to consider factors contributing to typhoid mortality (eg, healthcare access and antimicrobial resistance) in the global vaccination strategy.
Collapse
Affiliation(s)
- Nathan C Lo
- Division of Infectious Diseases and Geographic Medicine, California.,Division of Epidemiology, Stanford University School of Medicine, California
| | - Ribhav Gupta
- Division of Infectious Diseases and Geographic Medicine, California
| | - Jeffrey D Stanaway
- Institute for Health Metrics and Evaluation, University of Washington, Seattle
| | | | - Isaac I Bogoch
- Department of Medicine, University of Toronto, Washington, D. C.,Division of Internal Medicine, Toronto General Hospital, University Health Network, Toronto, Canada.,Division of Infectious Diseases, Toronto General Hospital, University Health Network, Toronto, Canada
| | - Stephen P Luby
- Division of Infectious Diseases and Geographic Medicine, California
| | - Jason R Andrews
- Division of Infectious Diseases and Geographic Medicine, California
| |
Collapse
|
10
|
Modeling and Cost Benefit Analysis to Guide Deployment of POC Diagnostics for Non-typhoidal Salmonella Infections with Antimicrobial Resistance. Sci Rep 2019; 9:11245. [PMID: 31375759 PMCID: PMC6677775 DOI: 10.1038/s41598-019-47359-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 07/05/2019] [Indexed: 12/03/2022] Open
Abstract
Invasive non-typhoidal Salmonella (NTS) is among the leading causes of blood stream infections in sub-Saharan Africa and other developing regions, especially among pediatric populations. Invasive NTS can be difficult to treat and have high case-fatality rates, in part due to emergence of strains resistant to broad-spectrum antibiotics. Furthermore, improper treatment contributes to increased antibiotic resistance and death. Point of care (POC) diagnostic tests that rapidly identify invasive NTS infection, and differentiate between resistant and non-resistant strains, may greatly improve patient outcomes and decrease resistance at the community level. Here we present for the first time a model for NTS dynamics in high risk populations that can analyze the potential advantages and disadvantages of four strategies involving POC diagnostic deployment, and the resulting impact on antimicrobial treatment for patients. Our analysis strongly supports the use of POC diagnostics coupled with targeted antibiotic use for patients upon arrival in the clinic for optimal patient and public health outcomes. We show that even the use of imperfect POC diagnostics can significantly reduce total costs and number of deaths, provided that the diagnostic gives results quickly enough that patients are likely to return or stay to receive targeted treatment.
Collapse
|
11
|
Environmental Foundations of Typhoid Fever in the Fijian Residential Setting. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 16:ijerph16132407. [PMID: 31284613 PMCID: PMC6651141 DOI: 10.3390/ijerph16132407] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/28/2019] [Accepted: 06/29/2019] [Indexed: 11/16/2022]
Abstract
Proximal characteristics and conditions in the residential setting deserve greater attention for their potential to influence typhoid transmission. Using a case-control design in Central Division, Republic of Fiji, we examined bacterial (coliform and Escherichia coli) contamination and chemical composition of water and soil as potential vehicles of exposure to Salmonella Typhi, combining observational analysis of residential living conditions, geospatial analysis of household locations, and factor analysis to explore multivariate associations with the risk of developing typhoid fever. Factors positively associated with typhoid infection related to drainage [phosphate (OR 4.235, p = 0.042) and E. coli concentrations (OR 2.248, p = 0.029) in toilet drainage soil, housing [external condition (OR 3.712, p < 0.001)], drinking water contamination (OR 2.732, p = 0.003) and sanitary condition (OR 1.973, p = 0.031). These five factors explained 42.5% of the cumulative variance and were significant in predicting typhoid infection. Our results support the hypothesis that a combination of spatial and biophysical attributes of the residential setting influence the probability of typhoid transmission; in this study, factors associated with poor drainage, flooding, and sanitary condition increase local exposure to contaminated water and soil, and thereby infection. These findings extend testing of causal assumptions beyond the immediate domestic domain, enhance the scope of traditional case control epidemiology and allow greater specificity of interventions at the scale of the residential setting.
Collapse
|
12
|
Perkins TA, Reiner RC, España G, ten Bosch QA, Verma A, Liebman KA, Paz-Soldan VA, Elder JP, Morrison AC, Stoddard ST, Kitron U, Vazquez-Prokopec GM, Scott TW, Smith DL. An agent-based model of dengue virus transmission shows how uncertainty about breakthrough infections influences vaccination impact projections. PLoS Comput Biol 2019; 15:e1006710. [PMID: 30893294 PMCID: PMC6443188 DOI: 10.1371/journal.pcbi.1006710] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 04/01/2019] [Accepted: 12/11/2018] [Indexed: 01/26/2023] Open
Abstract
Prophylactic vaccination is a powerful tool for reducing the burden of infectious diseases, due to a combination of direct protection of vaccinees and indirect protection of others via herd immunity. Computational models play an important role in devising strategies for vaccination by making projections of its impacts on public health. Such projections are subject to uncertainty about numerous factors, however. For example, many vaccine efficacy trials focus on measuring protection against disease rather than protection against infection, leaving the extent of breakthrough infections (i.e., disease ameliorated but infection unimpeded) among vaccinees unknown. Our goal in this study was to quantify the extent to which uncertainty about breakthrough infections results in uncertainty about vaccination impact, with a focus on vaccines for dengue. To realistically account for the many forms of heterogeneity in dengue virus (DENV) transmission, which could have implications for the dynamics of indirect protection, we used a stochastic, agent-based model for DENV transmission informed by more than a decade of empirical studies in the city of Iquitos, Peru. Following 20 years of routine vaccination of nine-year-old children at 80% coverage, projections of the proportion of disease episodes averted varied by a factor of 1.76 (95% CI: 1.54-2.06) across the range of uncertainty about breakthrough infections. This was equivalent to the range of vaccination impact projected across a range of uncertainty about vaccine efficacy of 0.268 (95% CI: 0.210-0.329). Until uncertainty about breakthrough infections can be addressed empirically, our results demonstrate the importance of accounting for it in models of vaccination impact.
Collapse
Affiliation(s)
- T. Alex Perkins
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, MD, United States of America
| | - Robert C. Reiner
- Fogarty International Center, National Institutes of Health, Bethesda, MD, United States of America
- Department of Epidemiology and Biostatistics, Indiana University, Bloomington, IN, United States of America
| | - Guido España
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | - Quirine A. ten Bosch
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | - Amit Verma
- Department of Biostatistics and Bioinformatics, Emory University, Atlanta, GA
| | - Kelly A. Liebman
- Department of Entomology and Nematology, University of California, Davis, CA, United States of America
| | - Valerie A. Paz-Soldan
- Department of Global Community Health and Behavioral Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, United States of America
| | - John P. Elder
- Institute for Behavioral and Community Health, Graduate School of Public Health, San Diego State University, San Diego, CA, United States of America
| | - Amy C. Morrison
- Department of Entomology and Nematology, University of California, Davis, CA, United States of America
| | - Steven T. Stoddard
- Institute for Behavioral and Community Health, Graduate School of Public Health, San Diego State University, San Diego, CA, United States of America
| | - Uriel Kitron
- Fogarty International Center, National Institutes of Health, Bethesda, MD, United States of America
- Department of Environmental Sciences, Emory University, Atlanta, GA, United States of America
| | - Gonzalo M. Vazquez-Prokopec
- Fogarty International Center, National Institutes of Health, Bethesda, MD, United States of America
- Department of Environmental Sciences, Emory University, Atlanta, GA, United States of America
| | - Thomas W. Scott
- Fogarty International Center, National Institutes of Health, Bethesda, MD, United States of America
- Department of Entomology and Nematology, University of California, Davis, CA, United States of America
| | - David L. Smith
- Fogarty International Center, National Institutes of Health, Bethesda, MD, United States of America
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, United States of America
| |
Collapse
|
13
|
Woroszyło C, Choi B, Healy Profitós J, Lee J, Garabed R, Rempala GA. Modeling household transmission dynamics: Application to waterborne diarrheal disease in Central Africa. PLoS One 2018; 13:e0206418. [PMID: 30403729 PMCID: PMC6221320 DOI: 10.1371/journal.pone.0206418] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Accepted: 10/13/2018] [Indexed: 11/25/2022] Open
Abstract
Introduction We describe a method for analyzing the within-household network dynamics of a disease transmission. We apply it to analyze the occurrences of endemic diarrheal disease in Cameroon, Central Africa based on observational, cross-sectional data available from household health surveys. Methods To analyze the data, we apply formalism of the dynamic SID (susceptible-infected-diseased) process that describes the disease steady-state while adjusting for the household age-structure and environment contamination, such as water contamination. The SID transmission rates are estimated via MCMC method with the help of the so-called synthetic likelihood approach. Results The SID model is fitted to a dataset on diarrhea occurrence from 63 households in Cameroon. We show that the model allows for quantification of the effects of drinking water contamination on both transmission and recovery rates for household diarrheal disease occurrence as well as for estimation of the rate of silent (unobserved) infections. Conclusions The new estimation method appears capable of genuinely capturing the complex dynamics of disease transmission across various human, animal and environmental compartments at the household level. Our approach is quite general and can be used in other epidemiological settings where it is desirable to fit transmission rates using cross-sectional data. Software sharing The R-scripts for carrying out the computational analysis described in the paper are available at https://github.com/cbskust/SID.
Collapse
Affiliation(s)
- Casper Woroszyło
- Mathematical Biosciences Institute, The Ohio State University, Columbus, 43210 Ohio, United States of America
| | - Boseung Choi
- Department of National Statistics, Korea University, Sejong, 30019, Republic of Korea
| | - Jessica Healy Profitós
- Division of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, 43210 Ohio, United States of America
| | - Jiyoung Lee
- Division of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, 43210 Ohio, United States of America
- Department of Food Science and Technology, The Ohio State University, Columbus, 43210 Ohio, United States of America
| | - Rebecca Garabed
- Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, 43210 Ohio, United States of America
| | - Grzegorz A. Rempala
- Mathematical Biosciences Institute, The Ohio State University, Columbus, 43210 Ohio, United States of America
- Division of Biostatistics, College of Public Health, The Ohio State University, Columbus, 43210 Ohio, United States of America
- * E-mail:
| |
Collapse
|
14
|
Liu Z, Lao J, Zhang Y, Liu Y, Zhang J, Wang H, Jiang B. Association between floods and typhoid fever in Yongzhou, China: Effects and vulnerable groups. ENVIRONMENTAL RESEARCH 2018; 167:718-724. [PMID: 30241731 DOI: 10.1016/j.envres.2018.08.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 08/24/2018] [Accepted: 08/27/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Little information about the effects of floods on typhoid fever is available in previous studies. This study aimed to examine the relationships between floods and typhoid fever and to identify the vulnerable groups in Yongzhou, China. METHODS Weekly typhoid fever data, flood data and meteorological data during the flood season (April to September) from 2005 to 2012 were collected for this study. A Poisson generalized linear model combined with a distributed lag non-linear model was conducted to quantify the lagged and cumulative effects of floods on typhoid fever, considering the confounding effects of long-term trend, seasonality, and meteorological variables. The model was also used to calculate risk ratios of floods for weekly typhoid fever cases among various subpopulations. RESULTS After adjusting for long-term trend, seasonality, and meteorological variables, floods were associated with an increased number of typhoid fever cases with a risk ratio of 1.46 (95% CI: 1.10-1.92) at 1-week lag and a cumulative risk ratio of 1.76 (95% CI: 1.21-2.57) at lag 0-1 weeks. Males, people aged 0-4 years old, people aged 15-64 years old, farmers, and children appeared to be more vulnerable than the others. CONCLUSIONS Our study indicates that floods could significantly increase the risks of typhoid fever with lag effects of 1 week in the study areas. Precautionary measures should be taken with a focus on the identified vulnerable groups in order to control the transmission of typhoid fever associated with floods.
Collapse
Affiliation(s)
- Zhidong Liu
- Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandong Province, People's Republic of China; Shandong University Climate Change and Health Center, Jinan, Shandong Province, People's Republic of China
| | - Jiahui Lao
- Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandong Province, People's Republic of China; Shandong University Climate Change and Health Center, Jinan, Shandong Province, People's Republic of China
| | - Ying Zhang
- School of Public Health, China Studies Centre, The University of Sydney, New South Wales, Australia
| | - Yanyu Liu
- Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandong Province, People's Republic of China; Shandong University Climate Change and Health Center, Jinan, Shandong Province, People's Republic of China
| | - Jing Zhang
- Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandong Province, People's Republic of China; Shandong University Climate Change and Health Center, Jinan, Shandong Province, People's Republic of China
| | - Hui Wang
- Department of Medical Administration, Second Hospital of Shandong University, No. 247 BeiYuan Road, 250033 Jinan, Shandong Province, People's Republic of China.
| | - Baofa Jiang
- Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandong Province, People's Republic of China; Shandong University Climate Change and Health Center, Jinan, Shandong Province, People's Republic of China.
| |
Collapse
|
15
|
Drolet M, Bénard É, Jit M, Hutubessy R, Brisson M. Model Comparisons of the Effectiveness and Cost-Effectiveness of Vaccination: A Systematic Review of the Literature. VALUE IN HEALTH : THE JOURNAL OF THE INTERNATIONAL SOCIETY FOR PHARMACOECONOMICS AND OUTCOMES RESEARCH 2018; 21:1250-1258. [PMID: 30314627 DOI: 10.1016/j.jval.2018.03.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 03/20/2018] [Accepted: 03/25/2018] [Indexed: 05/21/2023]
Abstract
OBJECTIVES To describe all published articles that have conducted comparisons of model-based effectiveness and cost-effectiveness results in the field of vaccination. Specific objectives were to 1) describe the methodologies used and 2) identify the strengths and limitations of the studies. METHODS We systematically searched MEDLINE and Embase databases for studies that compared predictions of effectiveness and cost-effectiveness of vaccination of two or more mathematical models. We categorized studies into two groups on the basis of their data source for comparison (previously published results or new simulation results) and performed a qualitative synthesis of study conclusions. RESULTS We identified 115 eligible articles (only 5% generated new simulations from the reviewed models) examining the effectiveness and cost-effectiveness of vaccination against 14 pathogens (69% of studies examined human papillomavirus, influenza, and/or pneumococcal vaccines). The goal of most of studies was to summarize evidence for vaccination policy decisions, and cost-effectiveness was the most frequent outcome examined. Only 33%, 25%, and 3% of studies followed a systematic approach to identify eligible studies, assessed the quality of studies, and performed a quantitative synthesis of results, respectively. A greater proportion of model comparisons using published studies followed a systematic approach to identify eligible studies and to assess their quality, whereas more studies using new simulations performed quantitative synthesis of results and identified drivers of model conclusions. Most comparative modeling studies concluded that vaccination was cost-effective. CONCLUSIONS Given the variability in methods used to conduct/report comparative modeling studies, guidelines are required to enhance their quality and transparency and to provide better tools for decision making.
Collapse
Affiliation(s)
- Mélanie Drolet
- Centre de recherche du CHU de Québec-Université Laval, Axe santé des populations et pratiques optimales en santé, Québec, Canada
| | - Élodie Bénard
- Centre de recherche du CHU de Québec-Université Laval, Axe santé des populations et pratiques optimales en santé, Québec, Canada
| | - Mark Jit
- Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK; Modelling and Economics Unit, Public Health England, London, UK
| | | | - Marc Brisson
- Centre de recherche du CHU de Québec-Université Laval, Axe santé des populations et pratiques optimales en santé, Québec, Canada; Université Laval, Québec, Canada; Department of Infectious Disease Epidemiology, Imperial College, London, UK.
| |
Collapse
|
16
|
Frempong SN, Sutton AJ, Davenport C, Barton P. Economic evaluation of typhoid - a review. Expert Rev Pharmacoecon Outcomes Res 2018; 18:601-607. [PMID: 30037288 DOI: 10.1080/14737167.2018.1503952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
INTRODUCTION To evaluate the potential economic value and likely impact of a hypothetical rapid test in its early stages of development requires the use of models. The model structure and the type of model (dynamic/static) to employ are key considerations. The aim of the review was to explore the literature on typhoid economic evaluations and to explore the types of models that have been previously adopted in this setting for test-treat evaluations and to capture data on model inputs that may be useful for a de novo model. AREAS COVERED A systematic review was conducted to identify economic evaluations focused on typhoid in established literature databases. Eight studies were identified and included for narrative synthesis. The review has revealed that there have been relatively few economic evaluations that have focused on typhoid fever, all of which have focused on the impact of interventions at the population level (vaccination) but not the individual level (test-treat strategies). EXPERT COMMENTARY Under certain circumstances, either a static model or a transmission dynamic model may be appropriate in the evaluation of an intervention for typhoid fever. Typhoid test-treat modeling represents a gray area where further work is needed.
Collapse
Affiliation(s)
- Samuel N Frempong
- a Institute of Applied Health Research, Health Economics Unit , University of Birmingham , Birmingham , UK
| | - Andrew J Sutton
- b Faculty of Medicine and Health , Leeds Institute of Health Sciences, University of Leeds , Leeds , UK.,c NHIR Diagnostic Evidence Co-operative Leeds , Leeds , UK
| | - Clare Davenport
- a Institute of Applied Health Research, Health Economics Unit , University of Birmingham , Birmingham , UK
| | - Pelham Barton
- a Institute of Applied Health Research, Health Economics Unit , University of Birmingham , Birmingham , UK
| |
Collapse
|
17
|
Nickerson KP, Senger S, Zhang Y, Lima R, Patel S, Ingano L, Flavahan WA, Kumar DKV, Fraser CM, Faherty CS, Sztein MB, Fiorentino M, Fasano A. Salmonella Typhi Colonization Provokes Extensive Transcriptional Changes Aimed at Evading Host Mucosal Immune Defense During Early Infection of Human Intestinal Tissue. EBioMedicine 2018; 31:92-109. [PMID: 29735417 PMCID: PMC6013756 DOI: 10.1016/j.ebiom.2018.04.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 04/02/2018] [Accepted: 04/05/2018] [Indexed: 12/29/2022] Open
Abstract
Commensal microorganisms influence a variety of host functions in the gut, including immune response, glucose homeostasis, metabolic pathways and oxidative stress, among others. This study describes how Salmonella Typhi, the pathogen responsible for typhoid fever, uses similar strategies to escape immune defense responses and survive within its human host. To elucidate the early mechanisms of typhoid fever, we performed studies using healthy human intestinal tissue samples and "mini-guts," organoids grown from intestinal tissue taken from biopsy specimens. We analyzed gene expression changes in human intestinal specimens and bacterial cells both separately and after colonization. Our results showed mechanistic strategies that S. Typhi uses to rearrange the cellular machinery of the host cytoskeleton to successfully invade the intestinal epithelium, promote polarized cytokine release and evade immune system activation by downregulating genes involved in antigen sampling and presentation during infection. This work adds novel information regarding S. Typhi infection pathogenesis in humans, by replicating work shown in traditional cell models, and providing new data that can be applied to future vaccine development strategies.
Collapse
Affiliation(s)
- K P Nickerson
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States; Department of Pediatrics, Harvard Medical School, Harvard University, Boston, MA, United States.
| | - S Senger
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States; Department of Pediatrics, Harvard Medical School, Harvard University, Boston, MA, United States
| | - Y Zhang
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, United States
| | - R Lima
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States
| | - S Patel
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States
| | - L Ingano
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States
| | - W A Flavahan
- Department of Pathology, Massachusetts General Hospital, Boston, MA, United States
| | - D K V Kumar
- Department for the Neuroscience of Genetics and Aging, Massachusetts General Hospital, Boston, MA, United States
| | - C M Fraser
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, United States
| | - C S Faherty
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States; Department of Pediatrics, Harvard Medical School, Harvard University, Boston, MA, United States
| | - M B Sztein
- Center for Vaccine Development, Department of Pediatrics, University of Maryland, Baltimore, MD, United States
| | - M Fiorentino
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States; Department of Pediatrics, Harvard Medical School, Harvard University, Boston, MA, United States
| | - A Fasano
- Department of Pediatric Gastroenterology, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Boston, MA, United States; Department of Pediatrics, Harvard Medical School, Harvard University, Boston, MA, United States.
| |
Collapse
|
18
|
A cross-sectional seroepidemiological survey of typhoid fever in Fiji. PLoS Negl Trop Dis 2017; 11:e0005786. [PMID: 28727726 PMCID: PMC5549756 DOI: 10.1371/journal.pntd.0005786] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 08/08/2017] [Accepted: 07/06/2017] [Indexed: 12/26/2022] Open
Abstract
Fiji, an upper-middle income state in the Pacific Ocean, has experienced an increase in confirmed case notifications of enteric fever caused by Salmonella enterica serovar Typhi (S. Typhi). To characterize the epidemiology of typhoid exposure, we conducted a cross-sectional sero-epidemiological survey measuring IgG against the Vi antigen of S. Typhi to estimate the effect of age, ethnicity, and other variables on seroprevalence. Epidemiologically relevant cut-off titres were established using a mixed model analysis of data from recovering culture-confirmed typhoid cases. We enrolled and assayed plasma of 1787 participants for anti-Vi IgG; 1,531 of these were resident in mainland areas that had not been previously vaccinated against S. Typhi (seropositivity 32.3% (95%CI 28.2 to 36.3%)), 256 were resident on Taveuni island, which had been previously vaccinated (seropositivity 71.5% (95%CI 62.1 to 80.9%)). The seroprevalence on the Fijian mainland is one to two orders of magnitude higher than expected from confirmed case surveillance incidence, suggesting substantial subclinical or otherwise unreported typhoid. We found no significant differences in seropositivity prevalences by ethnicity, which is in contrast to disease surveillance data in which the indigenous iTaukei Fijian population are disproportionately affected. Using multivariable logistic regression, seropositivity was associated with increased age (odds ratio 1.3 (95% CI 1.2 to 1.4) per 10 years), the presence of a pit latrine (OR 1.6, 95%CI 1.1 to 2.3) as opposed to a septic tank or piped sewer, and residence in settlements rather than residential housing or villages (OR 1.6, 95% CI 1.0 to 2.7). Increasing seropositivity with age is suggestive of low-level endemic transmission in Fiji. Improved sanitation where pit latrines are used and addressing potential transmission routes in settlements may reduce exposure to S. Typhi. Widespread unreported infection suggests there may be a role for typhoid vaccination in Fiji, in addition to public health management of cases and outbreaks. Fiji has experienced a decade-long increase in typhoid fever cases, a potentially life-threatening systemic bacterial disease caused by Salmonella Typhi. We undertook a representative blood-serum community survey to measure antibodies (IgG) against the Vi antigen of Salmonella Typhi using a rigorous survey design. We found one in three residents of mainland, unvaccinated Fiji had detectable antibody against Vi. This was higher than would be expected from confirmed case notifications received by the national surveillance system. Additionally, similar antibody responses were detected in Fijians of all ethnicities, which contrasts to surveillance cases in which indigenous iTaukei Fijians were disproportionately affected. Serology on a Fijian island where a significant proportion of the population has been vaccinated found that three-quarters of residents were seropositive three years after the Vi-polysaccharide typhoid vaccination campaign. Importantly, in mainland participants, seroprevalence increased with age, suggesting long-standing, low-level, endemic transmission. Pit latrines were associated with seropositivity when compared with septic tanks, and settlements compared with residential housing. Very high antibody titres in a small percentage of participants may suggest carriage of Salmonella Typhi. The seroprevalence findings suggest eliminating typhoid from Fiji by focussing on cases and outbreaks alone will be challenging. Our results support typhoid vaccination and further development of water, sanitation and hygiene infrastructure in Fiji.
Collapse
|
19
|
Darton TC, Meiring JE, Tonks S, Khan MA, Khanam F, Shakya M, Thindwa D, Baker S, Basnyat B, Clemens JD, Dougan G, Dolecek C, Dunstan SJ, Gordon MA, Heyderman RS, Holt KE, Pitzer VE, Qadri F, Zaman K, Pollard AJ. The STRATAA study protocol: a programme to assess the burden of enteric fever in Bangladesh, Malawi and Nepal using prospective population census, passive surveillance, serological studies and healthcare utilisation surveys. BMJ Open 2017; 7:e016283. [PMID: 28674145 PMCID: PMC5726077 DOI: 10.1136/bmjopen-2017-016283] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
INTRODUCTION Invasive infections caused by Salmonella enterica serovar Typhi and Paratyphi A are estimated to account for 12-27 million febrile illness episodes worldwide annually. Determining the true burden of typhoidal Salmonellae infections is hindered by lack of population-based studies and adequate laboratory diagnostics.The Strategic Typhoid alliance across Africa and Asia study takes a systematic approach to measuring the age-stratified burden of clinical and subclinical disease caused by typhoidal Salmonellae infections at three high-incidence urban sites in Africa and Asia. We aim to explore the natural history of Salmonella transmission in endemic settings, addressing key uncertainties relating to the epidemiology of enteric fever identified through mathematical models, and enabling optimisation of vaccine strategies. METHODS/DESIGN Using census-defined denominator populations of ≥100 000 individuals at sites in Malawi, Bangladesh and Nepal, the primary outcome is to characterise the burden of enteric fever in these populations over a 24-month period. During passive surveillance, clinical and household data, and laboratory samples will be collected from febrile individuals. In parallel, healthcare utilisation and water, sanitation and hygiene surveys will be performed to characterise healthcare-seeking behaviour and assess potential routes of transmission. The rates of both undiagnosed and subclinical exposure to typhoidal Salmonellae (seroincidence), identification of chronic carriage and population seroprevalence of typhoid infection will be assessed through age-stratified serosurveys performed at each site. Secondary attack rates will be estimated among household contacts of acute enteric fever cases and possible chronic carriers. ETHICS AND DISSEMINATION This protocol has been ethically approved by the Oxford Tropical Research Ethics Committee, the icddr,b Institutional Review Board, the Malawian National Health Sciences Research Committee and College of Medicine Research Ethics Committee and Nepal Health Research Council. The study is being conducted in accordance with the principles of the Declaration of Helsinki and Good Clinical Practice. Informed consent was obtained before study enrolment. Results will be submitted to international peer-reviewed journals and presented at international conferences. TRIAL REGISTRATION NUMBER ISRCTN 12131979. ETHICS REFERENCES Oxford (Oxford Tropical Research Ethics Committee 39-15).Bangladesh (icddr,b Institutional Review Board PR-15119).Malawi (National Health Sciences Research Committee 15/5/1599).Nepal (Nepal Health Research Council 306/2015).
Collapse
Affiliation(s)
- Thomas C Darton
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Department of Paediatrics, Oxford Vaccine Group, University of Oxford, and the NIHR Oxford Biomedical Research Centre, Oxford, UK
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Medical School, Sheffield, UK
| | - James E Meiring
- Department of Paediatrics, Oxford Vaccine Group, University of Oxford, and the NIHR Oxford Biomedical Research Centre, Oxford, UK
| | - Susan Tonks
- Department of Paediatrics, Oxford Vaccine Group, University of Oxford, and the NIHR Oxford Biomedical Research Centre, Oxford, UK
| | | | - Farhana Khanam
- International Centre for Diarrhoeal Diseases Research, Dhaka, Bangladesh
| | - Mila Shakya
- Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
| | - Deus Thindwa
- Malawi Liverpool Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi
| | - Stephen Baker
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
- The Wellcome Trust Sanger Institute, Cambridgeshire, UK
| | - Buddha Basnyat
- Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
- Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - John D Clemens
- International Centre for Diarrhoeal Diseases Research, Dhaka, Bangladesh
- UCLA Fielding School of Public Health, Los Angeles, USA
| | - Gordon Dougan
- The Wellcome Trust Sanger Institute, Cambridgeshire, UK
| | - Christiane Dolecek
- Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
- Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand
| | - Sarah J Dunstan
- The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, Australia
| | - Melita A Gordon
- Malawi Liverpool Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi
- Institute of Infection and Global Health, University of Liverpool, Liverpool, UK
| | - Robert S Heyderman
- Malawi Liverpool Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi
- Division of Infection and Immunity, University College London, London, UK
| | - Kathryn E Holt
- Centre for Systems Genomics, University of Melbourne, Victoria, Australia
- Department of Biochemistry and Molecular Biology, University of Melbourne, Victoria, Australia
| | - Virginia E Pitzer
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, Connecticut, USA
| | - Firdausi Qadri
- International Centre for Diarrhoeal Diseases Research, Dhaka, Bangladesh
| | - K Zaman
- International Centre for Diarrhoeal Diseases Research, Dhaka, Bangladesh
| | - Andrew J Pollard
- Department of Paediatrics, Oxford Vaccine Group, University of Oxford, and the NIHR Oxford Biomedical Research Centre, Oxford, UK
| |
Collapse
|
20
|
Amicizia D, Arata L, Zangrillo F, Panatto D, Gasparini R. Overview of the impact of Typhoid and Paratyphoid fever. Utility of Ty21a vaccine (Vivotif®). JOURNAL OF PREVENTIVE MEDICINE AND HYGIENE 2017; 58:E1-E8. [PMID: 28515625 PMCID: PMC5432773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cases of diarrhoeal disease number from 1.7 to 5 billion per year worldwide. One of the main causes of diarrhoeal disease is typhoid fever, which is a potentially life-threatening multi-systemic illness. According to the most recent estimates, a total of 26.9 million typhoid fever episodes occurred in 2010. The geographical distribution of the disease differs widely; in developed countries, the incidence rate per 100,000 per year varies from < 0.1 to 0.3, and the disease mainly affects people who travel to endemic areas located in low- and middle-income countries. Low- and middle-income countries are mainly affected owing to the lack of clean water and proper sanitation. In the fight against this plague, prevention is fundamental, and vaccination against typhoid is an effective measure. Vivotif® is an oral live attenuated vaccine which contains a mutated strain of Salmonella (Ty21a) and reproduces the natural infection. The vaccine was first licensed in Europe in 1983 and in the US in 1989, and over the years it has proved efficacious and safe. It is indicated for adults and children from 5 years of age upwards. Specifically, in the most developed countries, vaccination is suggested for highrisk population groups and particularly for international travellers to destinations where the risk of contracting typhoid fever is high. It must also be borne in mind that international travel is increasing. Indeed, international tourist arrivals totalled 1,184 million in 2015 and, on the basis of current trends, international travel is expected to grow by 3-4% in 2017. Vivotif® appears to be a powerful means of disease prevention, the importance of which is highlighted by the spread of antibiotic-resistant strains of Salmonella typhy (S. typhi).
Collapse
Affiliation(s)
| | - L. Arata
- Correspondence: Lucia Arata, Department of Health Sciences, University of Genoa, Italy - Tel. +39 010 3538394 - E-mail:
| | | | | | | |
Collapse
|
21
|
Gaiarsa S, De Marco L, Comandatore F, Marone P, Bandi C, Sassera D. Bacterial genomic epidemiology, from local outbreak characterization to species-history reconstruction. Pathog Glob Health 2016; 109:319-27. [PMID: 26878934 DOI: 10.1080/20477724.2015.1103503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Bacteriology has embraced the next-generation sequencing revolution, swiftly moving from the time of single genome sequencing to the age of genomic epidemiology. Hundreds and now even thousands of genomes are being sequenced for single bacterial species, allowing unprecedented levels of resolution and insight in the evolution and epidemic diffusion of the main bacterial pathogens. Here, we present a review of some of the most recent and groundbreaking studies in this field.
Collapse
Affiliation(s)
- Stefano Gaiarsa
- 1 Struttura Complessa di Microbiologia e Virologia, Fondazione IRCCS Policlinico San Matteo , Pavia, Italy
| | | | | | | | | | | |
Collapse
|
22
|
Gingras G, Guertin MH, Laprise JF, Drolet M, Brisson M. Mathematical Modeling of the Transmission Dynamics of Clostridium difficile Infection and Colonization in Healthcare Settings: A Systematic Review. PLoS One 2016; 11:e0163880. [PMID: 27690247 PMCID: PMC5045168 DOI: 10.1371/journal.pone.0163880] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 09/15/2016] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND We conducted a systematic review of mathematical models of transmission dynamic of Clostridium difficile infection (CDI) in healthcare settings, to provide an overview of existing models and their assessment of different CDI control strategies. METHODS We searched MEDLINE, EMBASE and Web of Science up to February 3, 2016 for transmission-dynamic models of Clostridium difficile in healthcare settings. The models were compared based on their natural history representation of Clostridium difficile, which could include health states (S-E-A-I-R-D: Susceptible-Exposed-Asymptomatic-Infectious-Resistant-Deceased) and the possibility to include healthcare workers and visitors (vectors of transmission). Effectiveness of interventions was compared using the relative reduction (compared to no intervention or current practice) in outcomes such as incidence of colonization, CDI, CDI recurrence, CDI mortality, and length of stay. RESULTS Nine studies describing six different models met the inclusion criteria. Over time, the models have generally increased in complexity in terms of natural history and transmission dynamics and number/complexity of interventions/bundles of interventions examined. The models were categorized into four groups with respect to their natural history representation: S-A-I-R, S-E-A-I, S-A-I, and S-E-A-I-R-D. Seven studies examined the impact of CDI control strategies. Interventions aimed at controlling the transmission, lowering CDI vulnerability and reducing the risk of recurrence/mortality were predicted to reduce CDI incidence by 3-49%, 5-43% and 5-29%, respectively. Bundles of interventions were predicted to reduce CDI incidence by 14-84%. CONCLUSIONS Although CDI is a major public health problem, there are very few published transmission-dynamic models of Clostridium difficile. Published models vary substantially in the interventions examined, the outcome measures used and the representation of the natural history of Clostridium difficile, which make it difficult to synthesize results and provide a clear picture of optimal intervention strategies. Future modeling efforts should pay specific attention to calibration, structural uncertainties, and transparent reporting practices.
Collapse
Affiliation(s)
- Guillaume Gingras
- SP-POS, Centre de recherche du CHU de Québec-Université Laval, 1050 Chemin Sainte-Foy, Québec, Qc, Canada.,Départment de Médecine Sociale et Préventive, Université Laval, Québec, Qc, Canada
| | - Marie-Hélène Guertin
- SP-POS, Centre de recherche du CHU de Québec-Université Laval, 1050 Chemin Sainte-Foy, Québec, Qc, Canada.,Départment de Médecine Sociale et Préventive, Université Laval, Québec, Qc, Canada
| | - Jean-François Laprise
- SP-POS, Centre de recherche du CHU de Québec-Université Laval, 1050 Chemin Sainte-Foy, Québec, Qc, Canada
| | - Mélanie Drolet
- SP-POS, Centre de recherche du CHU de Québec-Université Laval, 1050 Chemin Sainte-Foy, Québec, Qc, Canada
| | - Marc Brisson
- SP-POS, Centre de recherche du CHU de Québec-Université Laval, 1050 Chemin Sainte-Foy, Québec, Qc, Canada.,Départment de Médecine Sociale et Préventive, Université Laval, Québec, Qc, Canada.,Department of Infectious Disease Epidemiology, Imperial College, London, United Kingdom
| |
Collapse
|
23
|
Principi N, Esposito S. Preventing invasive salmonellosis in children through vaccination. Expert Rev Vaccines 2016; 15:897-905. [PMID: 27140662 DOI: 10.1080/14760584.2016.1183484] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
INTRODUCTION Vaccination is an important strategy to control endemic enteric fever (EF) and to interrupt transmission during outbreaks. The main aim of this paper is to discuss the efficacy of available EF vaccines in children and to highlight novel vaccination possibilities against EF and non-typhoid invasive salmonelloses. AREAS COVERED Two types of typhoid vaccines are presently available in the industrialized world. One of these vaccines is administered parenterally and is based on the virulence-associated (Vi) capsular polysaccaride of Salmonella typhi. The second vaccine is based on a live attenuated strain of the pathogen and is given orally. In addition, a Vi-tetanus toxoid conjugated vaccine is currently licensed in India; however, it is not available anywhere else. Expert commentary: Unfortunately, only typhoid fever is addressed by the currently licensed typhoid vaccines. Moreover, they are unsuitable for infants and remain a possible aid for reducing the risk of EF only in older subjects. They should be used in developing countries with endemic EF. New vaccines able to confer long-term protection to subjects in the first years of life and those with immature immune systems could significantly reduce incidence rates of EF in younger children. Vi-conjugate preparations are promising solutions in this regard.
Collapse
Affiliation(s)
- Nicola Principi
- a Paediatric Highly Intensive Care Unit, Department of Pathophysiology and Transplantation , Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milan , Italy
| | - Susanna Esposito
- a Paediatric Highly Intensive Care Unit, Department of Pathophysiology and Transplantation , Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico , Milan , Italy
| |
Collapse
|
24
|
Lessler J, Cummings DAT. Mechanistic Models of Infectious Disease and Their Impact on Public Health. Am J Epidemiol 2016; 183:415-22. [PMID: 26893297 PMCID: PMC5006438 DOI: 10.1093/aje/kww021] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 01/19/2016] [Indexed: 12/29/2022] Open
Abstract
From the 1930s through the 1940s, Lowell Reed and Wade Hampton Frost used mathematical models and mechanical epidemic simulators as research tools and to teach epidemic theory to students at the Johns Hopkins Bloomberg School of Public Health (then the School of Hygiene and Public Health). Since that time, modeling has become an integral part of epidemiology and public health. Models have been used for explanatory and inferential purposes, as well as in planning and implementing public health responses. In this article, we review a selection of developments in the history of modeling of infectious disease dynamics over the past 100 years. We also identify trends in model development and use and speculate as to the future use of models in infectious disease dynamics.
Collapse
Affiliation(s)
| | - Derek A. T. Cummings
- Correspondence to Dr. Derek A. T. Cummings, Department of Biology, Emerging Pathogens Institute, University of Florida, P.O. Box 118525, 220 Bartram Hall, Gainesville, FL 32611-8525 (e-mail: )
| |
Collapse
|
25
|
Bakach I, Just MR, Gambhir M, Fung ICH. Typhoid transmission: a historical perspective on mathematical model development. Trans R Soc Trop Med Hyg 2015; 109:679-89. [PMID: 26396161 DOI: 10.1093/trstmh/trv075] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 08/13/2015] [Indexed: 11/13/2022] Open
Abstract
Mathematical models of typhoid transmission were first developed nearly half a century ago. To facilitate a better understanding of the historical development of this field, we reviewed mathematical models of typhoid and summarized their structures and limitations. Eleven models, published in 1971 to 2014, were reviewed. While models of typhoid vaccination are well developed, we highlight the need to better incorporate water, sanitation and hygiene interventions into models of typhoid and other foodborne and waterborne diseases. Mathematical modeling is a powerful tool to test and compare different intervention strategies which is important in the world of limited resources. By working collaboratively, epidemiologists and mathematicians should build better mathematical models of typhoid transmission, including pharmaceutical and non-pharmaceutical interventions, which will be useful in epidemiological and public health practice.
Collapse
Affiliation(s)
- Iurii Bakach
- Department of Mathematical Sciences, College of Science and Mathematics, Georgia Southern University, Statesboro, Georgia, USA
| | - Matthew R Just
- Department of Mathematical Sciences, College of Science and Mathematics, Georgia Southern University, Statesboro, Georgia, USA
| | - Manoj Gambhir
- Epidemiological Modelling Unit, Department of Epidemiology and Preventive Medicine, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia
| | - Isaac Chun-Hai Fung
- Department of Epidemiology, Jiann-Ping Hsu College of Public Health, Georgia Southern University, P.O. Box 8015, Statesboro 30460-8015, Georgia, USA
| |
Collapse
|
26
|
Abstract
Efficacious typhoid fever vaccines have been available for decades. Typhoid fever burden of disease estimates indicate a substantial burden of illness and death in low-resource areas. The World Health Organization has recommended that countries consider the use of typhoid vaccines for high-risk groups and populations, and for outbreak control. Despite this, typhoid vaccines are not widely used in endemic areas. By examining strategies to improve burden of disease data, use of transmission dynamic models, economic evaluations, vaccine strategies, and experiences with typhoid vaccine pilot projects, the papers in this supplement help to plot the path toward rational and wider use of typhoid vaccines.
Collapse
Affiliation(s)
- John A Crump
- Centre for International Health, University of Otago, Dunedin, New Zealand.
| |
Collapse
|