Effectiveness of typhoid vaccination in US travelers.

Typhoid vaccination is recommended in the United States before travel to countries where typhoid fever is endemic, though little information is available on its effectiveness in travelers. We estimated typhoid vaccination effectiveness (VE) by comparing vaccination status in cases of typhoid fever and paratyphoid fever (Salmonella Paratyphi A infection, against which typhoid vaccine offers no protection) reported in the United States. We included travelers to Southern Asia and excluded persons <2 years old and cases in which vaccination status was not reported. From 2008 through 2011, 744 eligible cases (602 typhoid, 142 paratyphoid A) were reported to CDC. Typhoid vaccination was reported for 5% (29/602) of typhoid patients and for 20% (29/142) of paratyphoid A patients. Estimated VE was 80% (95% confidence interval, 66-89%). Because of missing data, we could not estimate VE for specific vaccines. We demonstrated moderate effectiveness of typhoid vaccination in US travelers, supporting vaccination recommendations.