Short-term effectiveness and impact of Vaxchora vaccine during the 2024 cholera outbreak in Mayotte

Global cholera resurgence and vaccine shortage have driven the adoption of reactive one-dose strategies with killed oral cholera vaccines (OCVs). The live-attenuated vaccine CVD 103-HgR (Vaxchora) shows high efficacy in human challenge studies, but its real-world effectiveness in outbreaks is unknown. Here, we analyze the 2024 outbreak in Mayotte, focusing on Koungou village, which had high cholera incidence and vaccine uptake. We develop several stochastic models and calibrate them to daily cases by vaccination status. In total, 3354 individuals (71%) of Koungou’s at-risk population ( n = 4733) received CVD 103-HgR, and 77 cases were confirmed, with symptom onset between 19 April and 7 July 2024. At baseline, we estimate a basic reproduction number R₀ R 0 of 1.5 (95% credible interval (CrI): 1.2, 1.9) and a CVD 103-HgR effectiveness in preventing cholera of 87% (95% CrI: 74, 99), remaining between 75% and 91% across scenarios. Counterfactual simulations estimate 536 (95% CrI: 240, 824) cases averted at baseline, with a range of point estimates from 152 to 1228 across sensitivity analyses. Rapid single-dose CVD 103-HgR deployment is associated with high effectiveness during a real‑world outbreak, with a substantial but more uncertain population impact, supporting the inclusion of live-attenuated OCVs in reactive strategies when necessary.