Cholera vaccine field trials in east Pakistan. 1. Reaction and antigenicity studies.

Double-blind controlled cholera-vaccine trials were carried out in rural East Pakistan in 1963 and 1964. Pretrial studies indicated that a whole-cell cholera vaccine of high mouse protective potency, at a dose of 0.5 ml, produced an antibody response and reaction pattern consistent with use in such trials. A purified Ogawa antigen, given at a dose of 100 mug, elicited no adverse reactions and evoked both agglutinating and vibriocidal antibodies against both Inaba and Ogawa test suspensions.In the field, adverse reactions to the cholera vaccines occurred primarily among adults and were observed with both the whole-cell preparation and the purified Ogawa antigen. At the dose used in the field trials (0.4 ml), the reactions elicited by the whole-cell vaccine were acceptable to the population and no more marked than those following the locally prepared typhoid-paratyphoid vaccine. Delayed reactions to the whole-cell cholera vaccine were observed beginning 4 to 7 days after the vaccine was administered; the bulk of them (60%) did not interfere with work at any time; all resolved promptly; and none developed fluctuation or was associated with abscess formation.