Immune responses following one and two doses of the reformulated, bivalent, killed, whole-cell, oral cholera vaccine among adults and children in Kolkata, India: a randomized, placebo-controlled trial.

Immune responses after one and two doses of the reformulated killed oral cholera vaccine were measured in a double-blind, randomized, placebo-controlled trial of 77 adults aged 18-40 years and 77 children aged 1-17 years residing in Kolkata, India. 65% of adults and 87% of children and 46% of adults and 82% of children exhibited a > or =4-fold rise in serum Vibrio cholerae O1 vibriocidal antibody titers from baseline following dose 1 and 2, respectively. Responses to V. cholerae O139 were less pronounced but followed a similar pattern. We demonstrate that in a cholera-endemic area, the vaccine elicited vibriocidal responses after a single-dose of the vaccine.