Field trial of oral cholera vaccines in Bangladesh.

The protective efficacy of oral B subunit killed whole-cell (BS-WC) and killed whole-cell (WC) cholera vaccines was assessed in 63 498 Bangladeshi children aged 2-15 years and women aged over 15 years. Each received three doses of BS-WC, WC, or placebo in a randomised, double-blinded fashion. Surveillance for cases seeking medical care up to six months after the third dose revealed 26 cases of confirmed cholera in the placebo group, 4 cases in the BS-WC group (protective efficacy 85%; p less than 0.0001), and 11 cases in the WC group (protective efficacy 58%; p less than 0.01). For each vaccine protective efficacy was consistent in different age-groups (2-10 years versus greater than 10 years) and for different severities of cholera.