Background: Live oral cholera vaccines may protect against cholera in a manner similar to natural cholera infections. However, information on which to base these vaccines is limited.
Methods: The study was conducted in a cholera-endemic population in Bangladesh. Patients with cholera (index patients) detected between 1991 and 2000 were age-matched to 4 cholera-free controls and then followed up during the subsequent 3 years.
Results: El Tor cholera was associated with a 65% (95% confidence interval [CI], 37%-81%; P < .001) lower risk of a subsequent El Tor episode. Reduction of the risk of subsequent El Tor cholera was similar for children < 5 years and for older persons and was sustained during all 3 years of follow-up. Having El Tor Inaba cholera was associated with lower risks of both El Tor Inaba and El Tor Ogawa cholera, but having El Tor Ogawa cholera was associated only with a reduced risk of El Tor Ogawa cholera. O139 cholera was associated with a 63% (95% CI, -61% to 92%; P = .18) lower risk of subsequent O139 cholera, but there was no evidence of cross-protection between the O1 and O139 serogroups.
Conclusions: Live oral cholera vaccines designed to protect against the O1 and O139 serogroups should contain at least the Inaba serotype and strains of both serogroups.