Randomized placebo controlled human volunteer trial of a live oral cholera vaccine VA1.3 for safety and immune response

A live oral cholera vaccine developed from a non-toxigenic Vibrio cholerae O1 El Tor strain VA1.3 was tested in a double-blind randomized placebo controlled study for safety and immunogenicity in 304 men aged between 16 and 50 years from Kolkata, India. A dose of 5 × 109 CFU (n = 186) or a placebo (n = 116) containing the diluent buffer was administered. The vaccine did not elicit adverse events except in two vaccine recipients with mild diarrhoea and vomiting. None excreted the vaccine strain. Vibriocidal antibody response developed in 105/186 (57%) and 5/116 (4%) in vaccine and placebo recipients, respectively. In a subgroup, anti-CT antibody rose (≥2-folds) in 23/30 (77%) and 6/19 (32%) in vaccine and placebo recipients, respectively. These studies demonstrate that VA1.3 at a dose of 5 × 109 is safe and immunogenic in adults from a cholera endemic region.