Vaccination against Typhoid Fever
Outbreaks of chloramphenicol-resistant typhoid stimulated a search for alternative oral antibiotic therapies and accelerated efforts to develop a new generation of better-tolerated, efficacious typhoid vaccines. The efforts bore fruit when live oral S. Typhi vaccine strain Ty21a and parenteral Vi polysaccharide vaccine were licensed in the late 1980s and early 1990s. Despite extensive data documenting the safety, efficacy, and practicality of the Vi and Ty21a vaccines, these preparations have not been widely applied programmatically in developing countries. The limited use of the Vi vaccine has been partly due to doubts about the programmatic feasibility and effect of Vi vaccination in public health programs, as well as questions about whether the vaccine is protective in children between the ages of 2 and 5 years and whether it can confer herd immunity. According to the Sur et al. report, the Vi vaccine conferred an adjusted vaccine effectiveness in preschool children of 80% after two