A multi-country study of dengue vaccination strategies with Dengvaxia and a future vaccine candidate in three dengue-endemic countries: Vietnam, Thailand, and Colombia

The potential global cost-effectiveness of prospective Strep A vaccines and associated implementation efforts

Group A Streptococcus causes a wide range of diseases from relatively mild infections including pharyngitis to more severe illnesses such as invasive diseases and rheumatic heart disease (RHD). Our aim is to estimate the cost-effectiveness of a hypothetical Strep A vaccine on multiple disease manifestations at the global-level. Cost-effectiveness analyses were carried out by building on the potential epidemiological impact of vaccines that align with the WHO's Preferred Product Characteristics for Strep A vaccines. Maximum vaccination costs for a cost-effective vaccination strategy were estimated at the thresholds of 1XGDP per capita and health opportunity costs. The maximum cost per fully vaccinated person for Strep A vaccination to be cost-effective was $385-$489 in high-income countries, $213-$312 in upper-income-income countries, $74-$132 in lower-middle-income countries, and $37-$69 in low-income countries for routine vaccination at birth and 5 years of age respectively. While the threshold costs are sensitive to vaccine characteristics such as efficacy, and waning immunity, a cost-effective Strep A vaccine will lower morbidity and mortality burden in all income settings.

Prevention and control of dengue and Chikungunya in Colombia: A cost-effectiveness analysis

Background

Chikungunya and dengue are emerging diseases that have caused large outbreaks in various regions of the world. Both are both spread by Aedes aegypti and Aedes albopictus mosquitos. We developed a dynamic transmission model of chikungunya and dengue, calibrated to data from Colombia (June 2014 –December 2017).

Methodology/Principal findings

We evaluated the health benefits and cost-effectiveness of residual insecticide treatment, long-lasting insecticide-treated nets, routine dengue vaccination for children aged 9, catchup vaccination for individuals aged 10–19 or 10–29, and portfolios of these interventions. Model calibration resulted in 300 realistic transmission parameters sets that produced close matches to disease-specific incidence and deaths. Insecticide was the preferred intervention and was cost-effective. Insecticide averted an estimated 95 chikungunya cases and 114 dengue cases per 100,000 people, 61 deaths, and 4,523 disability-adjusted life years (DALYs). In sensitivity analysis, strategies that included dengue vaccination were cost-effective only when the vaccine cost was 14% of the current price.

Conclusions/Significance

Insecticide to prevent chikungunya and dengue in Colombia could generate significant health benefits and be cost-effective. Because of limits on diagnostic accuracy and vaccine efficacy, the cost of dengue testing and vaccination must decrease dramatically for such vaccination to be cost-effective in Colombia. The vectors for chikungunya and dengue have recently spread to new regions, highlighting the importance of understanding the effectiveness and cost-effectiveness of policies aimed at preventing these diseases.

Chikungunya and dengue are emerging diseases that have caused large outbreaks in various regions of the world. Both are both spread by Aedes aegypti and Aedes albopictus mosquitos. To evaluate the effectiveness and cost-effectiveness of interventions aimed at controlling either of these diseases, it is important to consider the potential effects on both diseases, as an intervention that reduces the mosquito population will reduce the spread of both diseases. We developed a dynamic transmission model of chikungunya and dengue, calibrated to data from Colombia. We evaluated the health benefits and cost-effectiveness of the following interventions: residual insecticide treatment, long-lasting insecticide-treated nets, routine dengue vaccination for children aged 9, catchup dengue vaccination for individuals aged 10–19 or 10–29, and portfolios of these interventions. In all vaccination scenarios, we considered testing for previous exposure to dengue. We found that insecticide to prevent chikungunya and dengue in Colombia could generate significant health benefits and be cost-effective. While the dengue vaccine was effective in preventing cases and deaths, costs of diagnostic testing and vaccination must decrease for dengue vaccination to be considered cost-effective.

The characteristics and trend of adverse events following immunization reported by information system in Jiangsu province, China, 2015-2018

OBJECTIVE

Adverse events following immunization is an important factor influencing public trust in vaccination. Publicizing its incidence timely can increase public trust. The aim of this study is to describe the incidence and characteristics of adverse events following immunization in Jiangsu province of China from 2015 to 2018.

METHODS

All information of adverse events following immunization (AEFIs) was gained from Jiangsu Province Vaccination Integrated Service Management Information System. The reported AEFI trend was analyzed using Chi-square test.

RESULTS

A total of 77,980 AEFI cases were reported through the AEFI system; Among which, 77,731 were classified as non-serious AEFI cases and 249 were serious AEFI cases. The male to female ratio was 1.31:1, cases less than 7 years old accounted for 97.7%. The total estimated AEFI rate was 62.70/100,000 doses. By severity, 60.75/100,000, 4.46/100,000 and 0.11/100,000 AEFI cases were common vaccine reaction, rare vaccine reaction, and serious rare vaccine reaction, respectively. The top two serious AEFI were thrombocytopenic purpura and febrile. The incidence rates showed the increasing trend and the linear trend of the increasing incidence rates passed the significant test at 0.05 levels.

CONCLUSION

The sensitivity of AEFI monitoring in Jiangsu Province is increasing and higher than the national average and most countries. The majority of AEFI cases were common adverse reactions, while the serious vaccine reactions caused by vaccines were extremely low. To elevate the sensitivity of AEFI surveillance may reduce the incidence of developing serious AEFI cases.

On the Use of Markov Models in Pharmacoeconomics: Pros and Cons and Implications for Policy Makers

We present an overview of the main methodological features and the goals of pharmacoeconomic models that are classified in three major categories: regression models, decision trees, and Markov models. In particular, we focus on Markov models and define a semi-Markov model on the cost utility of a vaccine for Dengue fever discussing the key components of the model and the interpretation of its results. Next, we identify some criticalities of the decision rule arising from a possible incorrect interpretation of the model outcomes. Specifically, we focus on the difference between median and mean ICER and on handling the willingness-to-pay thresholds. We also show that the life span of the model and an incorrect hypothesis specification can lead to very different outcomes. Finally, we analyse the limit of Markov model when a large number of states is considered and focus on the implementation of tools that can bypass the lack of memory condition of Markov models. We conclude that decision makers should interpret the results of these models with extreme caution before deciding to fund any health care policy and give some recommendations about the appropriate use of these models.

Time varying methods to infer extremes in dengue transmission dynamics

Dengue is an arbovirus affecting global populations. Frequent outbreaks occur, especially in equatorial cities such as Singapore, where year-round tropical climate, large daily influx of travelers and population density provide the ideal conditions for dengue to transmit. Little work has, however, quantified the peaks of dengue outbreaks, when health systems are likely to be most stretched. Nor have methods been developed to infer differences in exogenous factors which lead to the rise and fall of dengue case counts across extreme and non-extreme periods. In this paper, we developed time varying extreme mixture (tvEM) methods to account for the temporal dependence of dengue case counts across extreme and non-extreme periods. This approach permits inference of differences in climatic forcing across non-extreme and extreme periods of dengue case counts, quantification of their temporal dependence as well as estimation of thresholds with associated uncertainties to determine dengue case count extremities. Using tvEM, we found no evidence that weather affects dengue case counts in the near term for non-extreme periods, but that it has non-linear and mixed signals in influencing dengue through tvEM parameters in the extreme periods. Using the most appropriate tvEM specification, we found that a threshold at the 70^th (95% credible interval 41.1, 83.8) quantile is optimal, with extreme events of 526.6, 1052.2 and 1183.6 weekly case counts expected at return periods of 5, 50 and 75 years. Weather parameters at a 1% scaled increase was found to decrease the long-run expected case counts, but larger increases would lead to a drastic expected rise from the baseline correspondingly. The tvEM approach can provide valuable inference on the extremes of time series, which in the case of infectious disease notifications, allows public health officials to understand the likely scale of outbreaks in the long run.

Dengue is an arbovirus affecting populations across much of the globe. Frequent outbreaks occur, especially in equatorial cities such as Singapore, where the year-round tropical climate, large daily influx of travelers and population density provide the ideal conditions for dengue transmission. Little work has however quantified the peaks of dengue outbreaks, when health systems are likely to be most stretched. Nor have methods been developed to infer differences in exogenous factors which lead to the rise and fall of dengue case counts across extreme and non extreme periods. In this paper, we developed time varying extreme mixture (tvEM) methods to account for the temporal dependence of dengue case counts across extreme and non-extreme periods. tvEM is able to infer differences in climatic forcing across non-extreme and extreme periods of dengue case counts, their temporal dependence as well as estimate suitable thresholds with associated uncertainties to determine dengue case count extremities. Using tvEM, we found no evidence that weather affects dengue case counts in the near term for non extreme periods, but has non-linear and mixed signals in influencing dengue through tvEM parameters in the extreme periods. Using the most appropriate tvEM specification, we found that a high percentile threshold is estimated, with dengue outbreak events far larger than currently observed to be expected in 5, 50 and 75 years. Weather parameters at a 1% scaled increase was found to decrease the long-run expected case counts, but larger increases would lead to a drastic expected rise from the baseline correspondingly. tvEM can provide valuable inference on the extremes of time series, which in the case of infectious disease data, allows public health officials to understand factors and the likely scale of infectious disease outbreaks in the long run.

Hidden heterogeneity and its influence on dengue vaccination impact

The CYD-TDV vaccine was recently developed to combat dengue, a mosquito-borne viral disease that afflicts millions of people each year throughout the tropical and subtropical world. Its rollout has been complicated by recent findings that vaccinees with no prior exposure to dengue virus (DENV) experience an elevated risk of severe disease in response to their first DENV infection subsequent to vaccination. As a result of these findings, guidelines for use of CYD-TDV now require serological screening prior to vaccination to establish that an individual does not fall into this high-risk category. These complications mean that the public health impact of CYD-TDV vaccination is expected to be higher in areas with higher transmission. One important practical difficulty with tailoring vaccination policy to local transmission contexts is that DENV transmission is spatially heterogeneous, even at the scale of neighborhoods or blocks within a city. This raises the question of whether models based on data that average over spatial heterogeneity in transmission could fail to capture important aspects of CYD-TDV impact in spatially heterogeneous populations. We explored this question with a deterministic model of DENV transmission and CYD-TDV vaccination in a population comprised of two communities with differing transmission intensities. Compared to the full model, a version of the model based on the average of the two communities failed to capture benefits of targeting the intervention to the high-transmission community, which resulted in greater impact in both communities than we observed under even coverage. In addition, the model based on the average of the two communities substantially overestimated impact among vaccinated individuals in the low-transmission community. In the event that the specificity of serological screening is not high, this result suggests that models that ignore spatial heterogeneity could overlook the potential for harm to this segment of the population.

A recombinant platform for flavivirus vaccines and diagnostics using chimeras of a new insect-specific virus

Flaviviruses such as dengue, yellow fever, Zika, West Nile, and Japanese encephalitis virus present substantial global health burdens. New vaccines are being sought to address safety and manufacturing issues associated with current live attenuated vaccines. Here, we describe a new insect-specific flavivirus, Binjari virus, which was found to be remarkably tolerant for exchange of its structural protein genes (prME) with those of the aforementioned pathogenic vertebrate-infecting flaviviruses (VIFs). Chimeric BinJ/VIF-prME viruses remained replication defective in vertebrate cells but replicated with high efficiency in mosquito cells. Cryo-electron microscopy and monoclonal antibody binding studies illustrated that the chimeric BinJ/VIF-prME virus particles were structurally and immunologically similar to their parental VIFs. Pilot manufacturing in C6/36 cells suggests that high yields can be reached up to 10^9.5 cell culture infectious dose/ml or ≈7 mg/liter. BinJ/VIF-prME viruses showed utility in diagnostic (microsphere immunoassays and ELISAs using panels of human and equine sera) and vaccine applications (illustrating protection against Zika virus challenge in murine IFNAR^-/- mouse models). BinJ/VIF-prME viruses thus represent a versatile, noninfectious (for vertebrate cells), high-yield technology for generating chimeric flavivirus particles with low biocontainment requirements.

A review of the economic evidence of Aedes-borne arboviruses and Aedes-borne arboviral disease prevention and control strategies

Introduction: Aedes-borne arboviruses contributes substantially to the disease and cost burden.Areas covered: We performed a systematic review of the economic evidence surrounding aedes-borne arboviruses and strategies to prevent and control these diseases to inform disease control policy decisions and research directions. We searched four databases covering an 18-year period (2000-2018) to identify arboviral disease-related cost of illness studies, cost studies of vector control and prevention strategies, cost-effectiveness analyses and cost-benefit analyses. We identified 74 published studies that revealed substantial global total costs in yellow fever virus and dengue virus ranging from 2.1 to 57.3 billion USD. Cost studies of vector control and surveillance programs are limited, but a few studies found that costs of vector control programs ranged from 5.62 to 73.5 million USD. Cost-effectiveness evidence was limited across Aedes-borne diseases, but generally found targeted dengue vaccination programs cost-effective. This review revealed insufficient economic evidence for vaccine introduction and implementation of surveillance and vector control programs.Expert opinion: Evidence of the economic burden of aedes-borne arboviruses and the economic impact of strategies for arboviral disease prevention and control is critical to inform policy decisions and to secure continued financial support for these preventive and control measures.

A Direct from Blood/Plasma Reverse Transcription-Polymerase Chain Reaction for Dengue Virus Detection in Point-of-Care Settings

Infection with dengue virus (DENV) is widespread across tropical regions and can result in severe disease. Early diagnosis is important both for patient management and to differentiate infections that present with similar symptoms, such as malaria, chikungunya, and Zika. Rapid diagnostic tests that are used presently for point-of-care detection of DENV antigens lack the sensitivity of molecular diagnostics that detect viral RNA. However, no molecular diagnostic test for DENV is available for use in field settings. In this study, we developed and validated a reverse transcription-polymerase chain reaction (RT-PCR) for the detection of DENV adapted for use in field settings. Reverse transcription-polymerase chain reaction was performed directly from plasma samples without RNA extraction. The assay detected all four serotypes of DENV spiked into blood or plasma. Our RT-PCR does not cross-react with pathogens that cause symptoms that overlap with dengue infection. The test performed equally well in a conventional laboratory qPCR instrument and a small, low-cost portable instrument that can be used in a field setting. The lower limit of detection for the assay was 1 × 10⁴ genome copy equivalents/mL in blood. Finally, we validated our test using 126 archived patient samples. The sensitivity of our RT-PCR was 76.7% (95% CI: 65.8-87.9%) on the conventional instrument, and 78.3% (95% CI: 65.8-87.9%) on the field instrument, when compared with the RealStar Dengue RT-PCR Kit 2.0. The molecular test described here is user-friendly, low-cost, and can be used in regions with limited laboratory capabilities.

Systematic review of health economic evaluation studies of dengue vaccines

OBJECTIVES

To review the literature on economic evaluation of dengue vaccination to produce evidence to support a local cost-effectiveness study and to subsidize the decision to introduce a dengue vaccine in the Brazilian National Immunization Program.

METHODS

We systematically searched multiple databases (MEDLINE (via PubMed), EMBASE, SCOPUS, NHS Economic Evaluation Database (NHS EED), HTA Database (via Centre for Reviews and Dissemination - CRD) and LILACS), selecting full HEEs of dengue vaccine. Two independent reviewers screened articles for relevance and extracted the data. The methodology for the quality reporting was assessed using CHEERS checklist. We performed a qualitative narrative synthesis.

RESULTS

Thirteen studies conducted in Asian and Latin America countries were reviewed. All studies were favorable to the incorporation of the vaccine. However, the assumptions and values assumed for vaccine efficacy, safety and duration of protection, as well as the choice of the study population and the type of model used in the analyses, associated to an insufficient reporting of the methodological steps, affect the validity of the studies' results. The quality reporting appraisal showed that the majority (8/13) of the studies reported less than 55% of the CHEERS checklists' items.

CONCLUSIONS

This systematic review shows that the economic evaluation of dengue vaccination did not adhere to key recommended general methods for economic evaluation. The presented cost-effectiveness results should not be transferred to other countries. It is recommended to conduct studies with local epidemiological and cost data, as well as assumptions about vaccination that reflect the results observed in clinical trials.

A multi-country study of the economic burden of dengue fever based on patient-specific field surveys in Burkina Faso, Kenya, and Cambodia

BACKGROUND

Dengue fever is a rapidly growing public health problem in many parts of the tropics and sub-tropics in the world. While there are existing studies on the economic burden of dengue fever in some of dengue-endemic countries, cost components are often not standardized, making cross-country comparisons challenging. Furthermore, no such studies have been available in Africa.

METHODS/PRINCIPAL FINDINGS

A patient-specific survey questionnaire was developed and applied in Burkina Faso, Kenya, and Cambodia in a standardized format. Multiple interviews were carried out in order to capture the entire cost incurred during the period of dengue illness. Both private (patient's out-of-pocket) and public (non-private) expenditure were accessed to understand how the economic burden of dengue is distributed between private and non-private payers. A substantial number of dengue-confirmed patients were identified in all three countries: 414 in Burkina Faso, 149 in Kenya, and 254 in Cambodia. The average cost of illness for dengue fever was $26 (95% CI $23-$29) and $134 (95% CI $119-$152) per inpatient in Burkina Faso and Cambodia, respectively. In the case of outpatients, the average economic burden per episode was $13 (95% CI $23-$29) in Burkina Faso and $23 (95% CI $19-$28) in Kenya. Compared to Cambodia, public contributions were trivial in Burkina Faso and Kenya, reflecting that a majority of medical costs had to be directly borne by patients in the two countries.

CONCLUSIONS/SIGNIFICANCE

The cost of illness for dengue fever is significant in the three countries. In particular, the current study sheds light on the potential economic burden of the disease in Burkina Faso and Kenya where existing evidence is sparse in the context of dengue fever, and underscores the need to achieve Universal Health Coverage. Given the availability of the current (CYD-TDV) and second-generation dengue vaccines in the near future, our study outcomes can be used to guide decision makers in setting health policy priorities.

Feasibility and willingness to pay for dengue vaccine in the threat of dengue fever outbreaks in Vietnam

BACKGROUND

The escalation of dengue fever (DF) cases in recent years and the occurrence of a large-scale DF outbreak in 2017 underline the importance of dengue vaccines in Vietnam. Given the potential benefits of the dengue vaccines and the need for copayment by the private sector, this study aims to evaluate the willingness to pay (WTP) for the dengue vaccines in patients with DF in Northern Vietnam.

METHODS

A cross-sectional study was conducted on 330 in-and-out patients with DF admitted to the Bach Mai Hospital. We used the contingent valuation method to evaluate the WTP for dengue vaccines. Socioeconomic and clinical characteristics were also investigated. Multivariate interval and logistic regression models were used to estimate the average amount of WTP and identify the factors associated with the WTP.

RESULTS

Around 77.3% patients were willing to pay an average amount of US$ 67.4 (95% CI=57.4-77.4) for the vaccine. People of higher ages, those having health insurance, those traveling in the past 15 days or suffering from anxiety/depression were less likely to be willing to pay for the dengue vaccine. However, people having a longer duration of DF or having problems with mobility were positively associated with WTP for the dengue vaccine. Patients educated to more than high school levels (Coeff.=31.31; 95% CI=3.26-59.35), those in the richest quintile (Coeff.=62.76; 95% CI=25.40; 100.13), or those having a longer duration of the disease (Coeff.=6.18; 95% CI=0.72-11.63) were willing to pay a higher amount.

CONCLUSION

This study highlights a relatively high rate and amount of WTP for the dengue vaccine among patients with DF. Psychological counseling services as well as educational campaigns should be undertaken to improve the WTP for the vaccine. Moreover, government subsidies should be given to increase the coverage of the vaccine in the future, especially for the poor.