The primary aim of this project is to determine changes in the vibriocidal geometric mean titers (GMT) in subjects who receive the second dose of oral cholera vaccine (OCV) at different intervals: 2 weeks, or 6 months following the first dose of vaccine. Secondary aims include a) vibriocidal antibody response rates in subjects who receive OCV at 2 weeks or 6 months following the first dose of vaccine, b) age specific serum vibriocidal GMTs following the second dose among participants given the second dose of OCV at intervals of 2 weeks or 6 months following the first dose of vaccine, c) GMT and antibody response rates of Immunoglobulin A (IgA) and Immunoglobulin G (IgG) anti-lipopolysaccharide (anti-LPS) as measured by ELISA following the second dose among participants given the second dose of OCV at intervals of 2 weeks or 6 months following the first dose of vaccine. Our hypothesis is that the vibriocidal GMT following the second dose, when given after 6 months will not be inferior to the response when the second dose is given according to the standard interval of two weeks.