Efficacy of one or two doses of Ty21a Salmonella typhi vaccine in enteric-coated capsules in a controlled field trial

Robert E. Black, Myron M. Levine, Catterine Ferreccio, Mary Lou Clements, Claudio Lanata, James Rooney, Rene Germanier, Typhoid Committee Chilean Typhoid Committee

Research output: Contribution to journalArticlepeer-review


Typhoid fever remains an important public health problem in many areas of the world and an effective, non-reactogenic vaccine would be useful to control this disease. An attenuated Salmonella typhi strain (Ty21a), which has shown promise in previous trials, was evaluated in a controlled field trial in Santiago, Chile. In this trial, 82 543 schoolchildren were randomly assigned to receive one or two doses of Ty21a vaccine in enteric-coated capsules or placebo. The enteric-coated vaccine formulation was well tolerated and practical for mass oral immunization. In the first two years of surveillance, 213 cases of bacteriologically-confirmed typhoid fever were found in schoolchildren participating in the trial; annual rates in the placebo group were 139 and 227 per 100 000. Vaccine efficacy in the first two years after vaccination was 59% for two doses and 29% for one dose; no efficacy was found 3-5 years after vaccination. These results indicate that it will be necessary to identify a vaccine formulation and schedule for Ty21a S. typhi that is practical and provides high level protection for > 2 years.

Original languageEnglish (US)
Pages (from-to)81-84
Number of pages4
Issue number1
StatePublished - Feb 1990
Externally publishedYes


  • Salmonella typhi
  • enteric-coated capsule
  • typhoid fever
  • vaccine

ASJC Scopus subject areas

  • Molecular Medicine
  • Immunology and Microbiology(all)
  • veterinary(all)
  • Public Health, Environmental and Occupational Health
  • Infectious Diseases

Fingerprint Dive into the research topics of 'Efficacy of one or two doses of Ty21a Salmonella typhi vaccine in enteric-coated capsules in a controlled field trial'. Together they form a unique fingerprint.

Cite this