Ty21a live oral typhoid vaccine and prevention of paratyphoid fever caused by Salmonella enterica serovar paratyphi B

Myron M. Levine, Catterine Ferreccio, Robert E. Black, Rosanna Lagos, Oriana San Martin, William C. Blackwelder

Research output: Contribution to journalArticle


In randomized, controlled field trials in Area Norte and Area Occidente of Santiago, Chile, 2 (Norte) or 3 (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%; P = .019).

Original languageEnglish (US)
Pages (from-to)S24-S28
JournalClinical Infectious Diseases
Issue numberSUPPL. 1
StatePublished - Jul 15 2007


ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases

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