The impact and cost-effectiveness of controlling cholera through the use of oral cholera vaccines in urban Bangladesh: A disease modeling and economic analysis

Background: Cholera remains an important public health problem in major cities in Bangladesh, especially in slum areas. In response to growing interest among local policymakers to control this disease, this study estimated the impact and cost-effectiveness of preventive cholera vaccination over a ten-year period in a high-risk slum population in Dhaka to inform decisions about the use of oral cholera vaccines as a key tool in reducing cholera risk in such populations. Methodology/Principal findings: Assuming use of a two-dose killed whole-cell oral cholera vaccine to be produced locally, the number of cholera cases and deaths averted was estimated for three target group options (1–4 year olds, 1–14 year olds, and all persons 1+), using cholera incidence data from Dhaka, estimates of vaccination coverage rates from the literature, and a dynamic model of cholera transmission based on data from Matlab, which incorporates herd effects. Local estimates of vaccination costs minus savings in treatment costs, were used to obtain incremental cost-effectiveness ratios for one- and ten-dose vial sizes. Vaccinating 1–14 year olds every three years, combined with annual routine vaccination of children, would be the most cost-effective strategy, reducing incidence in this population by 45% (assuming 10% annual migration), and costing was $823 (2015 USD) for single dose vials and $591 (2015 USD) for ten-dose vials per disability-adjusted life year (DALY) averted. Vaccinating all ages one year and above would reduce incidence by >90%, but would be 50% less cost-effective ($894–1,234/DALY averted). Limiting vaccination to 1–4 year olds would be the least cost-effective strategy (preventing only 7% of cases and costing $1,276-$1,731/DALY averted), due to the limited herd effects of vaccinating this small population and the lower vaccine efficacy in this age group. Conclusions/Significance: Providing cholera vaccine to slum populations in Dhaka through periodic vaccination campaigns would significantly reduce cholera incidence and inequities, and be especially cost-effective if all 1–14 year olds are targeted. Author summary: While oral cholera vaccines are increasingly being used in the past few years, mainly to curtail or preempt cholera outbreaks, they have yet to be used on a large scale to control endemic cholera in a high-burden country like Bangladesh. This study examines the potential impact on disease and value of vaccinating slum dwellers in Dhaka (and by extension in other cities), who are among those at highest-risk of getting the disease. This analysis suggests that, despite the modest efficacy and limited duration of protection of existing vaccines, mass cholera vaccination can have a significant impact on reducing cholera incidence in the entire population–including those not vaccinated–as a result of herd effects–and can be a cost-effective means of controlling the disease, especially until more long-term measures, such as improved water and sanitation infrastructure, are put in place. These results should assist policymakers and potential donors in determining whether and how to use these vaccines in Bangladesh to control the disease amongst its most vulnerable populations.