Ty21a live oral typhoid vaccine and prevention of paratyphoid fever caused by Salmonella enterica Serovar Paratyphi B.
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).
Levine
Myron M
MM
Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD 21201, USA. mlevine@medicine.umaryland.edu
Ferreccio
Catterine
C
Black
Robert E
RE
Lagos
Rosanna
R
San Martin
Oriana
O
Blackwelder
William C
WC
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
D011135:Polysaccharides, Bacterial; C072772:Ty21a typhoid vaccine; D014436:Typhoid-Paratyphoid Vaccines; D014613:Vaccines, Attenuated