Single-Dose, Inactivated Oral Cholera Vaccine

The development of an oral cholera vaccine represents a major advance in curbing epidemics caused by Vibrio cholerae. Two prior clinical trials demonstrated vaccine efficacy with a two-dose regimen of one of the vaccines that have been studied. Recognizing that data suggested an immunogenic response after only one dose of this vaccine, and that a single-dose vaccine would be more practical during a cholera epidemic that can occur following certain natural disasters, researchers conducted a randomized, placebo-controlled trial in Bangladesh. The killed vaccine was purchased from the manufacturer, and the trial was done in urban slums where endemic cholera is seen, particularly among children. Nonpregnant residents ≥1 year of age were eligible for enrollment. The primary outcome was vaccine protective efficacy, based on culture-confirmed cholera that occurred between 7 days and 6 months after vaccine dosing.

Overall, 204,700 residents were included in the analysis, and patient- and community-related variables were clinically similar between treatment arms. All cases were due to V. cholerae O1 El Tor biotype. The vaccine protective efficacy varied according to participants' age, although not significantly. Against all cholera presentations, for those 1 to 4 years of age, 5 to 14 years, and 15 years or more, efficacy was 16% (95% confidence interval, −49–53%), 63% (95% CI, −39%–90%), and 56% (95% CI, 16%–77%), respectively. The rate and types of adverse events did not differ between vaccine and placebo recipients. The authors conclude that the vaccine was efficacious in children aged 5 years or older and in adults.