title: Ty21a live oral typhoid vaccine and prevention of paratyphoid fever caused by Salmonella enterica Serovar Paratyphi B.
abstract: 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).
authors.affiliation: Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD 21201, USA. mlevine@medicine.umaryland.edu
authors.forename: Myron M
authors.initials: MM
authors.lastname: Levine
authors.forename: Catterine
authors.initials: C
authors.lastname: Ferreccio
authors.forename: Robert E
authors.initials: RE
authors.lastname: Black
authors.forename: Rosanna
authors.initials: R
authors.lastname: Lagos
authors.forename: Oriana
authors.initials: O
authors.lastname: San Martin
authors.forename: William C
authors.initials: WC
authors.lastname: Blackwelder
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002677:Chile / Q000453:epidemiology; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007115:Immunization Schedule; D015994:Incidence; D032541:Mass Vaccination; D010284:Paratyphoid Fever / Q000276:immunology / Q000517:prevention & control*; D011135:Polysaccharides, Bacterial / Q000276:immunology / Q000627:therapeutic use*; D012482:Salmonella paratyphi A / Q000276:immunology; D012484:Salmonella paratyphi B / Q000276:immunology*; D016896:Treatment Outcome; D014436:Typhoid-Paratyphoid Vaccines / Q000276:immunology / Q000627:therapeutic use*; D014613:Vaccines, Attenuated / Q000627:therapeutic use
chemical_list: D011135:Polysaccharides, Bacterial; C072772:Ty21a typhoid vaccine; D014436:Typhoid-Paratyphoid Vaccines; D014613:Vaccines, Attenuated