Efficacy of the Oral Cholera Vaccine Shanchol® in Preventing Cholera: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Abstract Background Oral cholera vaccines (OCVs) have become a crucial part of global strategies for cholera prevention, working alongside water, sanitation, and hygiene (WASH) initiatives. However, estimates of vaccine efficacy can vary depending on the context. This systematic review and meta-analysis aimed to assess the protective efficacy of the killed whole-cell bivalent OCV, Shanchol®, against laboratory-confirmed cholera. Methods In accordance with PRISMA 2020 guidelines, a comprehensive search was conducted in PubMed, Scopus, the Cochrane Library, EMBASE, and ISI Web of Science for randomized controlled trials (RCTs) published up to February 2023. Eligible studies compared two doses of Shanchol® with a placebo or no vaccination in either endemic or epidemic regions. Data were pooled using a random-effects model (DerSimonian–Laird method), with vaccine efficacy (VE) calculated using the formula VE = (1 − OR) × 100. The risk of bias was assessed using the Cochrane RoB 2 tool, and publication bias was examined through funnel plots. Findings Six RCTs conducted between 2011 and 2019 in India and Bangladesh met the inclusion criteria, involving a total of 627,982 participants (361,119 vaccinated and 266,863 controls). The pooled odds ratio was 0.41, translating to a vaccine efficacy of 59% (95% CI: 52%–65%; p < 0.001). Between-study heterogeneity was moderate (I² = 40%, p = 0.09). All trials showed statistically significant protection in favor of vaccination. The risk of bias was generally low, with funnel-plot symmetry indicating no significant publication bias. Conclusions Two doses of Shanchol® provide substantial and consistent protection against cholera, reducing the incidence of the disease by approximately 59%. These findings support the World Health Organization's recommendation to use OCVs as a complement to WASH interventions for both outbreak response and ongoing endemic control. Expanding vaccine access, combined with sustained improvements in sanitation and surveillance, is essential for achieving the Global Roadmap to 2030 goal of reducing cholera deaths by 90%.