The 1968-1969 cholera-vaccine field trial in rural east pakistan. Effectiveness of monovalent ogawa and inaba vaccines and a purified inaba antigen, with comparative results of serological and animal protection tests

In the field trial in 1968 in rural East Pakistan, monovalent whole-cell Ogawa and Inaba vaccines and a purified Inaba antigen were tested to determine the degree of protection induced by these vaccines against infection with the heterologous serotype of Vibrio cholerae, as well as the relationship between the level of protection, the results of animal protection tests, and human serological responses to the vaccines. During the first cholera season following inoculation, essentially all the cases were due to the Inaba serotype of V. cholerae; thus analysis was limited to effectiveness against that serotype. The monovalent Inaba vaccine and the purified Inaba antigen gave excellent protection in the first cholera season, which was primarily within 3 months after inoculation. The monovalent Ogawa vaccine was ineffective against Inaba cholera. The failure of the Ogawa vaccine to cross-protect against Inaba cholera paralleled the results of the tests of potency in mice but did not correlate with the serological studies, since recipients of the Ogawa vaccine developed substantial antiInaba vibriocidal antibody titers. The results indicate that vaccine-induced protection against cholera depends upon the development of type specific immunity.