IMPAIRED IMMUNE-RESPONSE TO NATURAL INFECTION AS A CORRELATE OF VACCINE FAILURE IN A FIELD TRIAL OF KILLED ORAL CHOLERA VACCINES

In a field trial carried out in 1985 in Matlab, Bangladesh, the author s evaluated whether subjects who developed Vibrio cholerae 01 infectio ns during the first year after earlier receipt of B subunit-killed who le cell (BS-WC) or killed whole cell-only (WC) oral cholera vaccines e xhibited deficient serum vibriocidal immune responses to these infecti ons. After severe V. cholerae 01 infections (n = 70) in subjects > 5 y ears of age, the age group in which both vaccines were efficacious, a 6.5 geometric mean-fold rise of serum vibriocidal antibodies was obser ved among vaccinees, compared with an 18.6 geometric mean-fold rise in placebo-recipients (p < 0.01). Depressions of serum vibriocidal respo nses among vaccinees were even more marked after asymptomatic infectio ns (n = 30): a 1.1 geometric mean-fold rise in vaccinees versus a 5.9 geometric mean-fold rise in placebo-recipients (p < 0.01). The authors conclude that subjects who failed to be protected by BS-WC and WC, de spite being in the age group for which these vaccines were protective, exhibited poor immune responses even to the vigorous stimulus of natu ral infection. These findings raise the possibility that immune hypore sponsiveness may limit the potential efficacy attainable by cholera va ccines in populations with endemic cholera.