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

• Published in: Clinical infectious diseases 2007-07, Vol.45 (Supplement-1), p.S24-S28
• Main Authors: Levine, Myron M., Ferreccio, Catterine, Black, Robert E., Lagos, Rosanna, Martin, Oriana San, Blackwelder, William C.
• Format: Article
• Language: English
• Subjects: Administration, Oral; Adolescent; Adult; Bacterial diseases; Bacterial diseases of the digestive system and abdomen; Biological and medical sciences; Capsules; Child; Child, Preschool; Chile - epidemiology; Clinical outcomes; Clinical trials; Disease prevention; Dose-Response Relationship, Immunologic; Epidemiology; Fever; Human bacterial diseases; Humans; Immunization Schedule; Incidence; Infectious diseases; Mass Vaccination; Medical sciences; Paratyphis; Paratyphoid fever; Paratyphoid Fever - immunology; Paratyphoid Fever - prevention & control; Pathology; Placebos; Polysaccharides, Bacterial - immunology; Polysaccharides, Bacterial - therapeutic use; Salmonella; Salmonella enterica; Salmonella paratyphi A - immunology; Salmonella paratyphi B - immunology; Salmonella typhi; Statistical analysis; Surveillance; Treatment Outcome; Typhoid; Typhoid fever; Typhoid-Paratyphoid Vaccines - immunology; Typhoid-Paratyphoid Vaccines - therapeutic use; Vaccination; Vaccines; Vaccines, Attenuated - therapeutic use
• ISSN: 1058-4838; 1537-6591
• DOI: 10.1086/518141

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).