Publications (65)232.42 Total impact
-
Article: Desirability for a typhoid fever vaccine among rural residents, Pemba Island, Tanzania.
[show abstract] [hide abstract]
ABSTRACT: BACKGROUND: Surveillance data indicate that Salmonella enterica serotype Typhi (S. Typhi) is a significant cause of morbidity and mortality in Africa. With limited anticipated short-term improvements in sanitation and water infrastructure, targeted vaccination campaigns may be an important prevention tool for typhoid fever. METHODS: A cross-sectional survey was conducted with 435 randomly selected households in four rural villages on Pemba Island, Tanzania. A dichotomous 'readiness to pay' variable was created to assess vaccine desirability. Data analyses included univariate and bivariate descriptive statistics and binary logistic regression. Bivariate outcomes (ANOVA, t-tests, and chi-square) and odds ratios with 95% confidence intervals are reported. RESULTS: A total of 66% respondents stated that they would pay for a typhoid fever vaccine in the future. Readiness to pay was not significantly associated with household expenditures. Readiness to pay was associated with use of local Primary Health Care Units (PHCUs) compared to use of cottage or district hospitals (OR 1.8 [95% CI, 1.2-2.7]: p=.007) and with knowledge of someone being sick from typhoid fever (OR 2.2 [95% CI, 1.0-4.5]: p=.039). Respondents perceiving prevention measures as more effective (OR 1.0 [95% CI, 1.0-1.2]: p=.009) were also more likely ready to pay. Preferred methods of communication of information about a typhoid fever vaccine included broadcasting via microphone ('miking'), radio, and door-to-door visits. CONCLUSIONS: With rapid increase in numbers of licensed and promising vaccines, policy makers and health administrators are faced with decisions regarding allocation of scarce health resources for competing interventions. Community residents need to be informed about diseases which may not be readily recognized, diagnosed, and treated. Perceived vulnerability to the disease may increase likelihood of vaccine desirability. A better local understanding of typhoid fever is needed for general prevention measures, increasing treatment access, and future vaccination campaigns.Vaccine 05/2013; · 3.77 Impact Factor -
Article: Herd protection by a bivalent-killed-whole-cell oral cholera vaccine in the slums of Kolkata, India.
[show abstract] [hide abstract]
ABSTRACT: Background. We evaluated the herd protection conferred by an oral cholera vaccine using two approaches: cluster design and geographic information systems (GIS) design.Methods. Residents living in 3,933 dwellings (clusters) in Kolkata, India were cluster-randomized to receive either cholera vaccine oral placebo. Non-pregnant residents, one year of age and older were invited to participate in the trial. Only the first episode of cholera detected for a subject between 14 and 1095 days after a second dose was considered. In the cluster design, indirect protection was assessed by comparing the incidence of cholera among non-participants in vaccine clusters versus those in placebo clusters. In the GIS analysis herd protection was assessed by evaluating association between vaccine coverage among population residing within 250 m around the household and the occurrence of cholera in that population.Results. Among 107,347 eligible residents, 66,990 received two-doses of either cholera vaccine or placebo. In the cluster design, the three-year data showed significant total protection (66% protection, 95%CI:50%-78%, p<.01) but no evidence of indirect protection. With the GIS approach, the risk of cholera among placebo recipients was inversely related to neighborhood level vaccine coverage, and the trend was highly significant (p<.01). This relationship held in multivariable models that also controlled for potentially confounding demographic variables (Hazard Ratio:0.94; 95% CI:0.90-0.98; p<.01).Conclusions. Indirect protection was evident in analyses using the GIS approach but not the cluster design approach, likely due to considerable transmission of cholera between clusters, which would vitiate herd protection in the cluster analyses.Clinical Infectious Diseases 01/2013; · 9.15 Impact Factor -
Article: Utilization and Accessibility of Healthcare on Pemba Island, Tanzania: Implications for Health Outcomes and Disease Surveillance for Typhoid Fever.
[show abstract] [hide abstract]
ABSTRACT: Salmonella enterica serotype Typhi (S. Typhi) was estimated to cause over 200,000 deaths and more than 21 million illnesses worldwide, including over 400,000 illnesses in Africa. The current study was conducted in four villages on Pemba Island, Zanzibar, in 2010. We present data on policy makers', health administrators', and village residents' and leaders' perceptions of typhoid fever, and hypothetical and actual health care use among village residents for typhoid fever. Qualitative data provided descriptions of home-based treatment practices and use of western pharmaceuticals, and actual healthcare use for culture-confirmed typhoid fever. Survey data indicate health facility use was associated with gender, education, residency, and perceptions of severity for symptoms associated with typhoid fever. Data have implications for education of policy makers and health administrators, design and implementation of surveillance studies, and community-based interventions to prevent disease outbreaks, decrease risks of complications, and provide information about disease recognition, diagnosis, and treatment.The American journal of tropical medicine and hygiene 12/2012; · 2.59 Impact Factor -
Article: Effectiveness of an oral cholera vaccine in Zanzibar: findings from a mass vaccination campaign and observational cohort study.
[show abstract] [hide abstract]
ABSTRACT: Zanzibar, in east Africa, has been severely and repeatedly affected by cholera since 1978. We assessed the effectiveness of oral cholera vaccination in high-risk populations in the archipelago to estimate the indirect (herd) protection conferred by the vaccine and direct vaccine effectiveness. We offered two doses of a killed whole-cell B-subunit cholera vaccine to individuals aged 2 years and older in six rural and urban sites. To estimate vaccine direct protection, we compared the incidence of cholera between recipients and non-recipients using generalised estimating equations with the log link function while controlling for potential confounding variables. To estimate indirect effects, we used a geographic information systems approach and assessed the association between neighbourhood-level vaccine coverage and the risk for cholera in the non-vaccinated residents of that neighbourhood, after controlling for potential confounding variables. This study is registered with ClinicalTrials.gov, number NCT00709410. Of 48 178 individuals eligible to receive the vaccine, 23 921 (50%) received two doses. Between February, 2009, and May, 2010, there was an outbreak of cholera, enabling us to assess vaccine effectiveness. The vaccine conferred 79% (95% CI 47-92) direct protection against cholera in participants who received two doses. Indirect (herd) protection was shown by a decrease in the risk for cholera of non-vaccinated residents within a household's neighbourhood as the vaccine coverage in that neighbourhood increased. Our findings suggest that the oral cholera vaccine offers both direct and indirect (herd) protection in a sub-Saharan African setting. Mass oral cholera immunisation campaigns have the potential to provide not only protection for vaccinated individuals but also for the unvaccinated members of the community and should be strongly considered for wider use. Because this is an internationally-licensed vaccine, we could not undertake a randomised placebo-controlled trial, but the absence of vaccine effectiveness against non-cholera diarrhoea indicates that the noted protection against cholera could not be explained by bias. Bill & Melinda Gates Foundation, Swedish International Development Cooperation Agency, and the South Korean Government.The Lancet Infectious Diseases 09/2012; 12(11):837-44. · 17.39 Impact Factor -
Article: The global burden of cholera.
[show abstract] [hide abstract]
ABSTRACT: To estimate the global burden of cholera using population-based incidence data and reports. Countries with a recent history of cholera were classified as endemic or non-endemic, depending on whether they had reported cholera cases in at least three of the five most recent years. The percentages of the population in each country that lacked access to improved sanitation were used to compute the populations at risk for cholera, and incidence rates from published studies were applied to groups of countries to estimate the annual number of cholera cases in endemic countries. The estimates of cholera cases in non-endemic countries were based on the average numbers of cases reported from 2000 to 2008. Literature-based estimates of cholera case-fatality rates (CFRs) were used to compute the variance-weighted average cholera CFRs for estimating the number of cholera deaths. About 1.4 billion people are at risk for cholera in endemic countries. An estimated 2.8 million cholera cases occur annually in such countries (uncertainty range: 1.4-4.3) and an estimated 87,000 cholera cases occur in non-endemic countries. The incidence is estimated to be greatest in children less than 5 years of age. Every year about 91,000 people (uncertainty range: 28,000 to 142,000) die of cholera in endemic countries and 2500 people die of the disease in non-endemic countries. The global burden of cholera, as determined through a systematic review with clearly stated assumptions, is high. The findings of this study provide a contemporary basis for planning public health interventions to control cholera.Bulletin of the World Health Organisation 03/2012; 90(3):209-218A. · 4.64 Impact Factor -
Article: New-generation vaccines against cholera.
[show abstract] [hide abstract]
ABSTRACT: Cholera is a major global health problem, causing approximately 100,000 deaths annually, about half of which occur in sub-Saharan Africa. Although early-generation parenteral cholera vaccines were abandoned as public health tools owing to their limited efficacy, newer-generation oral cholera vaccines have attractive safety and protection profiles. Both killed and live oral vaccines have been licensed, although only killed oral vaccines are currently manufactured and available. These killed oral vaccines not only provide direct protection to vaccinated individuals, but also confer herd immunity. The combination of direct vaccine protection and vaccine herd immunity effects makes these vaccines highly cost-effective and, therefore, attractive for use in developing countries. Administration of these oral vaccines does not require qualified medical personnel, which makes their use practical--even in developing countries. Although new-generation oral cholera vaccines should not be considered in isolation from other preventive approaches, especially improved water quality and sanitation, they represent important tools in the public health armamentarium to control both endemic and epidemic cholera.Nature Reviews Gastroenterology & Hepatology 11/2011; 8(12):701-10. · 8.10 Impact Factor -
Article: Impact of Vi vaccination on spatial patterns of typhoid fever in the slums of Kolkata, India.
[show abstract] [hide abstract]
ABSTRACT: A mass typhoid Vi vaccination campaign was carried out among approximately 60,000 slum residents of Kolkata, India. This study evaluated the impact of the campaign on spatial patterns of typhoid fever. Eighty contiguous residential groups of households in the study area were randomized to receive either a single dose of the Vi polysaccharide vaccine or a single dose of the inactivated hepatitis A vaccine as the control agent. Persons aged two years and older were eligible to receive the vaccine. Vaccine protection against typhoid fever was monitored for two years after vaccination at both outpatient and inpatient facilities serving the study population. Geographic analytic and mapping tools were used in the analysis. Spatial randomness of the disease was observed during the pre-vaccination period, which turned into a significant pattern after vaccination. The high-risk areas for typhoid were observed in the area dominated by the control clusters, and the low-risk areas were in the area dominated by the Vi clusters. Furthermore, the control clusters surrounded by the Vi clusters were low risk for typhoid fever. The results demonstrated the ability of mass vaccination to change the spatial patterns of disease through the creation of spatial barriers to transmission of the disease. Understanding and mapping the disease risk could be useful for designing a community-based vaccination strategy to control disease.Vaccine 09/2011; 29(48):9051-6. · 3.77 Impact Factor -
Article: Safety and immunogenicity study of a killed bivalent (O1 and O139) whole-cell oral cholera vaccine Shanchol, in Bangladeshi adults and children as young as 1 year of age.
[show abstract] [hide abstract]
ABSTRACT: Safety and immunogenicity study of an oral, killed, bivalent whole-cell, cholera vaccine, Shanchol was carried out in Bangladeshi participants. This study was conducted prior to initiating a feasibility study in Bangladesh. The double-blind, randomized placebo controlled study was carried out in adults (18-45 years), toddlers (2-5 years) and younger children (12-23 months). Two doses of the vaccine/placebo were given 14 days apart. Shanchol did not elicit major adverse events in any age group. Vibriocidal antibody responses in adults were 60% against Vibrio cholerae O1 Inaba, 72% against V. cholerae O1 Ogawa and 21% against V. cholerae O139. In toddlers, responses were 84%, 75% and 64% and in younger children it was 74%, 78% and 54% against Inaba, Ogawa and O139 serotypes. The responses in all ages were higher in vaccinees compared to pre-immune titers or to responses in placebo recipients (P<0.001). Plasma IgA antibody response to O1 Inaba LPS was seen in 61%, 73% and 45% of adults, toddlers and younger children, respectively. The safety and immunogenicity data for Shanchol is promising and warrants future use in large scale trial in cholera endemic areas, high risk Bangladeshi population and in other countries in the region.Vaccine 09/2011; 29(46):8285-92. · 3.77 Impact Factor -
Article: Natural cholera infection-derived immunity in an endemic setting.
[show abstract] [hide abstract]
ABSTRACT: Live oral cholera vaccines may protect against cholera in a manner similar to natural cholera infections. However, information on which to base these vaccines is limited. The study was conducted in a cholera-endemic population in Bangladesh. Patients with cholera (index patients) detected between 1991 and 2000 were age-matched to 4 cholera-free controls and then followed up during the subsequent 3 years. El Tor cholera was associated with a 65% (95% confidence interval [CI], 37%-81%; P < .001) lower risk of a subsequent El Tor episode. Reduction of the risk of subsequent El Tor cholera was similar for children < 5 years and for older persons and was sustained during all 3 years of follow-up. Having El Tor Inaba cholera was associated with lower risks of both El Tor Inaba and El Tor Ogawa cholera, but having El Tor Ogawa cholera was associated only with a reduced risk of El Tor Ogawa cholera. O139 cholera was associated with a 63% (95% CI, -61% to 92%; P = .18) lower risk of subsequent O139 cholera, but there was no evidence of cross-protection between the O1 and O139 serogroups. Live oral cholera vaccines designed to protect against the O1 and O139 serogroups should contain at least the Inaba serotype and strains of both serogroups.The Journal of Infectious Diseases 09/2011; 204(6):912-8. · 6.41 Impact Factor -
Article: New approaches to the assessment of vaccine herd protection in clinical trials.
[show abstract] [hide abstract]
ABSTRACT: Criteria for the introduction of new vaccines into routine public health practice are becoming increasingly stringent. For vaccines that are expensive and those that provide moderate protection, the ability to confer herd protection could be crucial to policy deliberations about vaccine introduction. Traditionally, herd protection has been assessed after a vaccine is introduced, delaying the availability of data on herd effects to inform decisions about vaccine introduction. New methodological developments now provide the possibility to assess herd protection before the introduction of a vaccine into public health programmes. One approach is a cluster-randomised trial, which allows assessment of herd protection in a way that minimises biases. Analysis of individually randomised trials by appropriately selected clusters created post hoc can also provide measurements of herd protection. Here we discuss the use of these designs, which can generate an improved evidence base at an early stage for making decisions about the introduction of new vaccines.The Lancet Infectious Diseases 06/2011; 11(6):482-7. · 17.39 Impact Factor -
Article: Cost of illness due to typhoid fever in five Asian countries
[show abstract] [hide abstract]
ABSTRACT: Objective To generate community-based estimates of the public (paid by the government) and private (paid by households) costs of blood culture-confirmed typhoid fever in Hechi, China; North Jakarta, Indonesia; Kolkata, India; Karachi, Pakistan and Hue, Vietnam.Methods To measure out-of-pocket costs of illness and lost earnings, families with culture-proven cases were surveyed 7, 14 and 90 days after onset of illness. Public costs of treatment were measured at local health facilities using a micro costing (bottom-up) method.Results The costs of hospitalized cases ranged from USD 129 in Kolkata to USD 432 in North Jakarta (hospitalization rates varied from 2% in Kolkata to 40% in Hechi) and the costs of non-hospitalized cases ranged from USD 13 in Kolkata to USD 67 in Hechi. Where costs were highest (Hechi, North Jakarta and Karachi), the bulk of the costs of hospitalized cases was borne by families, comprising up to 15% of annual household income.Conclusion Although these estimates may understate true costs due to the fact that higher quality treatment may have been provided earlier-than-usual, this multi-country community-based study contributes to evidence on the public and private costs of typhoid fever in developing countries. These cost estimates were used in a cost-effectiveness analysis of typhoid vaccines and will help policymakers respond to World Health Organization’s updated typhoid fever immunization recommendations.Objectif: Etablir des estimations communautaires des coûts publics (payés par le gouvernement) et privés (payés par les ménages) pour la fièvre typhoïde confirmée par la culture de sang à Hechi en Chine, dans le Nord Jakarta en Indonésie, à Kolkata en Inde, à Karachi au Pakistan et à Hue au Vietnam.Méthodes: Afin de mesurer les dépenses de la maladie payées directement de la poche et la perte de gain, les familles avec des cas confirmés par la culture ont été interrogées 7, 14 et 90 jours après l’apparition de la maladie. Les coûts publics de traitement ont été mesurés dans les services de santé locaux en utilisant une méthode à micro estimation (bottom-up).Résultats: Les coûts des cas hospitalisés variaient de 129 USD à Kolkata à 432 USD dans le Nord Jakarta (les taux d’hospitalisation variaient de 2%à Kolkata à 40%à Hechi) et les coûts des cas non hospitalisés variaient de 13 USD à Kolkata à 67 USD à Hechi. Là où les coûts étaient les plus élevés (Hechi, Nord Jakarta et Karachi), la plupart des coûts des cas d’hospitalisation ont été pris en charge par les familles, représentant jusqu’à 15% des revenus annuels des ménages.Conclusion: Bien que ces estimations puissent sous-estimer les coûts réels du fait qu’un traitement de meilleure qualité ait pu être administré plus tôt que d’habitude, cette étude communautaire multi-pays contribue à fournir des preuves sur les coûts publics et privés de la fièvre typhoïde dans les pays en développement. Ces estimations de coûts ont été utilisées dans une analyse coût-efficacité des vaccins contre la typhoïde et aideront les décideurs à répondre à la mise à jour des recommandations de vaccination de l’OMS contre la fièvre typhoïde.Objetivos: Generar estimativos de los costes públicos (pagados por el gobierno) y privados (pagados por los hogares) de los hemocultivos positivos para fiebre tifoidea en Hechi, China; Jakarta del norte, Indonesia; Kolkata, India; Karachi, Paquistán; y Hue, Vietnam.Métodos: Para medir los gastos de bolsillo de la enfermedad y los ingresos perdidos, se entrevistó a las familias con casos probados mediante cultivo a los 7, 14, y 90 días después del comienzo de la enfermedad. Los costes públicos del tratamiento se midieron en los centros sanitarios locales utilizando un método de microcostes (enfoque ascendente).Resultados: Los costes de los casos hospitalizados estaban entre USD 129 en Kolkata a USD 432 en Jakarta del norte (las tasas de hospitalización variaban del 2% en Kolkata al 40% en Hechi) y los costes de los casos no hospitalizados estaban entre USD 13 en Kolkata a USD 67 en Hechi. En aquellos lugares en los que los costes eran más altos (Hechi, Yakarta del norte y Karachi), la mayor parte del gasto de los casos hospitalizados era asumido por las familias, llegando a ser equivalente a hasta un 15% del ingreso anual del hogar.Conclusión: Aunque estos estimativos podrían estar subestimando los costes reales debido al hecho de que el tratamiento de mayor calidad podría haberse entregado más pronto de lo usual, este estudio multipaís, basado en la comunidad, contribuye a evidenciar los costes públicos y privados de la fiebre tifoidea en países en vías de desarrollo. Estos costes estimados se utilizaron en un análisis coste efectividad y ayudará a que aquellos que diseñan las políticas sanitarias puedan responder a la actualización de la OMS sobre las recomendaciones en lo que respecta a la inmunización para la fiebre tifoidea.Tropical Medicine & International Health 02/2011; 16(3):314 - 323. · 2.80 Impact Factor -
Article: Cost of illness due to typhoid fever in five Asian countries.
[show abstract] [hide abstract]
ABSTRACT: To generate community-based estimates of the public (paid by the government) and private (paid by households) costs of blood culture-confirmed typhoid fever in Hechi, China; North Jakarta, Indonesia; Kolkata, India; Karachi, Pakistan and Hue, Vietnam. To measure out-of-pocket costs of illness and lost earnings, families with culture-proven cases were surveyed 7, 14 and 90 days after onset of illness. Public costs of treatment were measured at local health facilities using a micro costing (bottom-up) method. The costs of hospitalized cases ranged from USD 129 in Kolkata to USD 432 in North Jakarta (hospitalization rates varied from 2% in Kolkata to 40% in Hechi) and the costs of non-hospitalized cases ranged from USD 13 in Kolkata to USD 67 in Hechi. Where costs were highest (Hechi, North Jakarta and Karachi), the bulk of the costs of hospitalized cases was borne by families, comprising up to 15% of annual household income. Although these estimates may understate true costs due to the fact that higher quality treatment may have been provided earlier-than-usual, this multi-country community-based study contributes to evidence on the public and private costs of typhoid fever in developing countries. These cost estimates were used in a cost-effectiveness analysis of typhoid vaccines and will help policymakers respond to World Health Organization's updated typhoid fever immunization recommendations.Tropical Medicine & International Health 01/2011; 16(3):314-23. · 2.80 Impact Factor -
Article: Ten years of the Global Alliance for Vaccines and Immunization: challenges and progress.
[show abstract] [hide abstract]
ABSTRACT: Diseases preventable by underused vaccines cause the death of approximately 3 million children per year. The Global Alliance for Vaccines and Immunization (GAVI) was launched 10 years ago to tackle this appalling situation.Nature Immunology 12/2010; 11(12):1069-72. · 26.01 Impact Factor -
Article: Suitable disk antimicrobial susceptibility breakpoints defining Salmonella enterica serovar Typhi isolates with reduced susceptibility to fluoroquinolones.
[show abstract] [hide abstract]
ABSTRACT: Infections with Salmonella enterica serovar Typhi isolates that have reduced susceptibility to ofloxacin (MIC ≥ 0.25 μg/ml) or ciprofloxacin (MIC ≥ 0.125 μg/ml) have been associated with a delayed response or clinical failure following treatment with these antimicrobials. These isolates are not detected as resistant using current disk susceptibility breakpoints. We examined 816 isolates of S. Typhi from seven Asian countries. Screening for nalidixic acid resistance (MIC ≥ 16 μg/ml) identified isolates with an ofloxacin MIC of ≥0.25 μg/ml with a sensitivity of 97.3% (253/260) and specificity of 99.3% (552/556). For isolates with a ciprofloxacin MIC of ≥0.125 μg/ml, the sensitivity was 92.9% (248/267) and specificity was 98.4% (540/549). A zone of inhibition of ≤28 mm around a 5-μg ofloxacin disc detected strains with an ofloxacin MIC of ≥0.25 μg/ml with a sensitivity of 94.6% (246/260) and specificity of 94.2% (524/556). A zone of inhibition of ≤30 mm detected isolates with a ciprofloxacin MIC of ≥0.125 μg/ml with a sensitivity of 94.0% (251/267) and specificity of 94.2% (517/549). An ofloxacin MIC of ≥0.25 μg/ml and a ciprofloxacin MIC of ≥0.125 μg/ml detected 74.5% (341/460) of isolates with an identified quinolone resistance-inducing mutation and 81.5% (331/406) of the most common mutant (carrying a serine-to-phenylalanine mutation at codon 83 in the gyrA gene). Screening for nalidixic acid resistance or ciprofloxacin and ofloxacin disk inhibition zone are suitable for detecting S. Typhi isolates with reduced fluoroquinolone susceptibility.Antimicrobial Agents and Chemotherapy 12/2010; 54(12):5201-8. · 4.84 Impact Factor -
Article: Evaluation of the Widal tube agglutination test for the diagnosis of typhoid fever among children admitted to a rural hdospital in Tanzania and a comparison with previous studies
[show abstract] [hide abstract]
ABSTRACT: Abstract Background The diagnosis of typhoid fever is confirmed by culture of Salmonella enterica serotype Typhi ( S. typhi ). However, a more rapid, simpler, and cheaper diagnostic method would be very useful especially in developing countries. The Widal test is widely used in Africa but little information exists about its reliability. Methods We assessed the performance of the Widal tube agglutination test among febrile hospitalized Tanzanian children. We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of various anti-TH and -TO titers using culture-confirmed typhoid fever cases as the "true positives" and all other febrile children with blood culture negative for S. typhi as the "true negatives." Results We found that 16 (1%) of 1,680 children had culture-proven typhoid fever. A single anti-TH titer of 1:80 and higher was the optimal indicator of typhoid fever. This had a sensitivity of 75%, specificity of 98%, NPV of 100%, but PPV was only 26%. We compared our main findings with those from previous studies. Conclusion Among febrile hospitalized Tanzanian children with a low prevalence of typhoid fever, a Widal titer of ≥ 1:80 performed well in terms of sensitivity, specificity, and NPV. However a test with improved PPV that is similarly easy to apply and cost-efficient is desirable.BMC Infectious Diseases. 01/2010; -
Article: Evaluating investments in typhoid vaccines in two slums in Kolkata, India.
[show abstract] [hide abstract]
ABSTRACT: New-generation vaccines against typhoid fever have the potential to reduce the burden of disease in areas where the disease is endemic. The case for public expenditure on typhoid Vi polysaccharide vaccines for two low-income, high-incidence slums (Narkeldanga and Tiljala) in Kolkata, India, was examined. Three measures of the economic benefits of the vaccines were used: private and public cost-of-illness (COI) avoided; avoided COI plus mortality risk-reduction benefits; and willingness-to-pay (WTP) derived from stated preference (contingent valuation) studies conducted in Tiljala in 2004. Benefits and costs were examined from a social perspective. The study represents a unique opportunity to evaluate typhoid-vaccine programmes using a wealth of new site-specific epidemiological and economic data. Three typhoid-vaccination strategies (targeting only enrolled school children, targeting all children, and targeting adults and children) would most likely pass a social cost-benefit test, unless benefits are restricted to include only avoided COI. All three strategies would be considered 'very cost-effective' using the standard comparisons of cost per disability-adjusted life-year avoided with per-capita gross domestic product. However, at an average total cost per immunized person of approximately US$ 1.1, a typhoid-vaccination programme would absorb a sixth of existing public-sector spending on health (on a per-capita basis) in India. Because there appears to be significant private economic demand for typhoid vaccines, the Government could design a financially-sustainable programme with user-fees. The results show that a programme where adults pay a higher fee to subsidize vaccines for children (who have higher incidence) would avoid more cases than a uniform user-fee and still achieve revenue-neutrality.Journal of Health Population and Nutrition 12/2009; 27(6):711-24. · 0.95 Impact Factor -
Article: Using private demand studies to calculate socially optimal vaccine subsidies in developing countries
[show abstract] [hide abstract]
ABSTRACT: Although it is well known that vaccines against many infectious diseases confer positive economic externalities via indirect protection, analysts have typically ignored possible herd protection effects in policy analyses of vaccination programs. Despite a growing literature on the economic theory of vaccine externalities and several innovative mathematical modeling approaches, there have been almost no empirical applications. The first objective of the paper is to develop a transparent, accessible economic framework for assessing the private and social economic benefits of vaccination. We also describe how stated preference studies (for example, contingent valuation and choice modeling) can be useful sources of economic data for this analytic framework. We demonstrate socially optimal policies using a graphical approach, starting with a standard textbook depiction of Pigouvian subsidies applied to herd protection from vaccination programs. We also describe nonstandard depictions that highlight some counterintuitive implications of herd protection that we feel are not commonly understood in the applied policy literature. We illustrate the approach using economic and epidemiological data from two neighborhoods in Kolkata, India. We use recently published epidemiological data on the indirect effects of cholera vaccination in Matlab, Bangladesh (Ali et al., 2005) for fitting a simple mathematical model of how protection changes with vaccine coverage. We use new data on costs and private demand for cholera vaccines in Kolkata, India, and approximate the optimal Pigouvian subsidy. We find that if the optimal subsidy is unknown, selling vaccines at full marginal cost may, under some circumstances, be a preferable second-best option to providing them for free. © 2009 by the Association for Public Policy Analysis and Management.Journal of Policy Analysis and Management 11/2009; 28(1):6-28. · 0.93 Impact Factor -
Article: Vaccine desirability during an effectiveness trial of the typhoid fever polysaccharide Vi vaccine in Kolkata India.
[show abstract] [hide abstract]
ABSTRACT: High rates of typhoid fever and the emergence of multi-drug resistant strains create a need for prevention efforts including vaccines. Socio-behavioral research can provide important data for participation in future trials and public health vaccination campaigns. A 3b phase clinical trial in Kolkata India including pre- and post-vaccination socio-behavioral surveys. 47.9% of respondents were male. Ward 29 respondents included 32.4% Hindu and Ward 30 respondents were 99.0% Hindu. Lower rates of participation were found among Muslim respondents and those with post high school education. Lack of information and negative information affected participation. Joint decision-making within households increased participation rates. seven hundred households were randomly selected 503 respondents (71.85%) completed both the pre- and post-closed-ended surveys. Data analysis included descriptive statistics, Pearson's chi-square tests, independent t-tests, and stepwise logistic regression analysis. Four open-ended questions were included in the survey. These qualitative data were coded and reviewed for common themes and patterns. Individuals' decisions to participate or not participate in a vaccine trial entail a balance between individual beliefs, household dynamics and socio-political influences. Efforts prior to vaccination trials need to develop strategies which address potential underlying mediators for belief systems as well as structural factors which may reinforce individuals' beliefs and perceptions about vaccination trials.Human vaccines 10/2009; 5(9):614-20. · 3.58 Impact Factor -
Article: Cost-effectiveness of new-generation oral cholera vaccines: a multisite analysis.
[show abstract] [hide abstract]
ABSTRACT: We evaluated the cost-effectiveness of a low-cost cholera vaccine licensed and used in Vietnam, using recently collected data from four developing countries where cholera is endemic. Our analysis incorporated new findings on vaccine herd protective effects. Using data from Matlab, Bangladesh, Kolkata, India, North Jakarta, Indonesia, and Beira, Mozambique, we calculated the net public cost per disability-adjusted life year avoided for three immunization strategies: 1) school-based vaccination of children 5 to 14 years of age; 2) school-based vaccination of school children plus use of the schools to vaccinate children aged 1 to 4 years; and 3) community-based vaccination of persons aged 1 year and older. We determined cost-effectiveness when vaccine herd protection was or was not considered, and compared this with commonly accepted cutoffs of gross domestic product (GDP) per person to classify interventions as cost-effective or very-cost effective. Without including herd protective effects, deployment of this vaccine would be cost-effective only in school-based programs in Kolkata and Beira. In contrast, after considering vaccine herd protection, all three programs were judged very cost-effective in Kolkata and Beira. Because these cost-effectiveness calculations include herd protection, the results are dependent on assumed vaccination coverage rates. Ignoring the indirect effects of cholera vaccination has led to underestimation of the cost-effectiveness of vaccination programs with oral cholera vaccines. Once these effects are included, use of the oral killed whole cell vaccine in programs to control endemic cholera meets the per capita GDP criterion in several developing country settings.Value in Health 09/2009; 12(6):899-908. · 2.19 Impact Factor -
Article: Modeling spatial heterogeneity of disease risk and evaluation of the impact of vaccination.
[show abstract] [hide abstract]
ABSTRACT: We reanalyzed data from a phase III trial for the killed oral cholera vaccine to test two hypotheses: there will be a greater impact of the vaccine in areas where there is a low force of infection, and the spatial pattern of disease transmission will change after a mass vaccination campaign. Spatial regression was used to test these hypotheses accounting for spatial heterogeneity in disease and vaccine coverage. The results of the analyses confirm both hypotheses. The paper also shows how spatial analysis can be used to understand the impact of vaccination when there are spatially heterogeneous disease distributions.Vaccine 07/2009; 27(28):3724-9. · 3.77 Impact Factor
Top co-authors
Top Journals
Institutions
-
2004–2013
-
International Vaccine Institute
Seoul, Seoul, South Korea
-
-
2011
-
RTI International
Durham, NC, USA
-
-
2009
-
Manchester Business School
Manchester, ENG, United Kingdom
-
-
2008–2009
-
University of Washington Seattle
Seattle, WA, USA -
University of North Carolina at Chapel Hill
- Department of Environmental Sciences and Engineering
Chapel Hill, NC, USA -
Aga Khan University Hospital, Karachi
Karachi, Sindh, Pakistan
-
-
2007
-
Children's Hospital of Michigan
Detroit, MI, USA -
National Institute of Hygiene and Epidemiology
Hà Nội, Thu Do Ha Noi, Vietnam -
University of Maryland, Baltimore
- Department of Medicine
Baltimore, MD, USA
-
-
2006
-
Eunice Kennedy Shriver National Institute of Child Health and Human Development
Rockville, MD, USA
-
-
2005
-
Guangdong Center for Disease Control and Prevention
Guangzhou, Guangdong Sheng, China
-
-
1989
-
University of Maryland-School of Medicine
Baltimore, MD, USA
-
