Real-world effectiveness of oral cholera vaccine amid fragility: A case-control study from Eastern Sudan, 2024

Cholera is a serious public health threat, especially in fragile conflict-affected areas. Reactive oral cholera vaccine (rOCV) during outbreaks is a key response strategy recommended by the World Health Organization. Sudan implemented a large-scale reactive campaign during 2024 cholera outbreak in Kassala State.

This unmatched case-control study was conducted between 6 and 26 October 2024 in Kassala locality, targeted by the national rOCV campaign using Euvichol-Plus. Data were collected through structured interviews using a pre-tested questionnaire, and analyzed in Epi Info 7 with logistic regression to estimate vaccine effectiveness and identify predictors of infection.

The mean age was significantly lower in cases (30.6 years, standard deviation = 20.8, P < 0.001). Cases had bigger households and multiple families per household (P < 0.001). Only 42.5% of cases used soap after defecation vs 97.5% of controls (odds ratio [OR] = 0.018), while 57% used only water (OR = 52.9). Street food consumption (OR = 4.04), funeral exposure (OR = 13.3), and family history (OR = 124.4) were strong predictors. OCV reduced infection odds by 93% (adjusted OR = 0.07, 95% confidence interval: 0.037-0.13, P < 0.001).

Findings reaffirm OCV effectiveness, but emphasize the need for sustainable investment in water sanitation, and hygiene (WASH), hygiene promotion, and risk communication in fragile settings.