Ty21a Live Oral Typhoid Vaccine and Prevention of Paratyphoid Fever Caused by Salmonella enterica

(Occidente) doses of live oral typhoid vaccine Ty21a in enteric-coated capsules conferred protection against confirmed Salmonella enterica serovar Typhi disease (53 % efficacy in Norte; 67 % efficacy in Occidente) during 3 years of follow-up. There was also a trend in each trial showing protection against S. enterica serovar Paratyphi B disease (56 % efficacy in Norte; 42 % efficacy in Occidente). To enhance statistical power, an analysis was performed using pooled data from the 2 trials; this pooling of data was justified by the following facts: epidemiologic surveillance and microbiological methods were identical, the trials overlapped during 22 of the 36 months of follow-up in each trial, the estimates of efficacy against paratyphoid B fever in the 2 trials were roughly similar, and the ratio of follow-up of vaccine recipients to control subjects in both trials was ∼1:1. In the pooled analysis, Ty21a conferred significant protection against paratyphoid B fever (efficacy, 49%; 95% confidence interval, 8%–73%;).Pp.019 Of the clinical enteric fevers that occur globally, ∼80% are caused by Salmonella enterica serovar Typhi (S. Ty-phi) and 20 % by S. enterica serovars Paratyphi A and B (S. Paratyphi A and B) [1]. Killed whole-cell par-enteral typhoid vaccines manufactured in the earl