title: Protective activity of Vi capsular polysaccharide vaccine against typhoid fever.
abstract: The protective efficacy against typhoid fever of a single intramuscular injection of 25 micrograms of the Vi capsular polysaccharide (CPS) was assessed in a randomised double-blind controlled trial. Vaccination of 11,384 children was followed by 21 months' surveillance. 47 blood-culture-proven cases of typhoid occurred in children who received meningococcal A + C CPS vaccine and 19 cases in those vaccinated with Vi CPS. Protective efficacy was 60% calculated from the day of vaccination and 64% from 6 weeks after vaccination. Surveillance also included 11,691 unvaccinated children; 173 cases occurred in this group. Protective efficacy in relation to the unvaccinated group was 77.4% and 81.0% after 21 months, calculated immediately and 6 weeks after vaccination, respectively. Vaccination was associated with minimum local side-effects, and an increase in anti-Vi antibodies occurred, as measured by radioimmunoassay and enzyme-linked immunosorbent assay. Antibody levels remained significantly raised at 6 and 12 months post vaccination. Vi CPS is thus a safe and effective means of typhoid vaccination.
mesh_terms: D000293:Adolescent; D000907:Antibodies, Bacterial / Q000032:analysis; D000942:Antigens, Bacterial / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology*; D001428:Bacterial Vaccines / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D002986:Clinical Trials as Topic; D004311:Double-Blind Method; D004797:Enzyme-Linked Immunosorbent Assay; D005069:Evaluation Studies as Topic; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011135:Polysaccharides, Bacterial / Q000276:immunology; D011863:Radioimmunoassay; D011897:Random Allocation; D012485:Salmonella typhi / Q000276:immunology*; D014435:Typhoid Fever / Q000276:immunology / Q000517:prevention & control*; D014436:Typhoid-Paratyphoid Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology*; D014611:Vaccination / Q000009:adverse effects
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D011135:Polysaccharides, Bacterial; D014436:Typhoid-Paratyphoid Vaccines; C043226:meningococcal group A polysaccharide; C037676:meningococcal group C polysaccharide