To investigate whether micronutrient supplementation could improve the vibriocidal antibody response of children to a killed oral cholera vaccine, 2-5-year-old children were randomly assigned to receive vitamin A and zinc (AZ group), vitamin A and a placebo (A group), zinc and a placebo (Z group), or both placebos (P group). All children received 2 doses of the vaccine. The number of children who had a у4-fold increase in vibriocidal antibody was significantly greater in the AZ group than in

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... P group ( ). Factorial P p .025-.028 analysis suggested that the proportion of children with a у4-fold increase in vibriocidal antibody titer was significantly greater in the zinc-supplemented groups than in the groups that did not receive zinc (P p ) and that vitamin A supplementation did not have a significant effect. Thus, supplementation with .013-.048 zinc improves seroconversion to vibriocidal antibody and, hence, has the potential to improve the efficacy of oral cholera vaccine in children. The protective efficacy of a killed oral cholera vaccine [1] and serum vibriocidal antibody levels [2], a marker of protection against cholera, have been found to be low in 2-5-year-old children (the age group most susceptible to cholera) in Bangladesh. Some vaccines stimulate a better immune response in populations in developed countries than in those in developing countries