title: Large-scale field trial of Ty21a live oral typhoid vaccine in enteric-coated capsule formulation.
abstract: Three doses, given within one week, of Ty21a attenuated Salmonella typhi oral vaccine in an enteric-coated formulation provided 67% efficacy for at least 3 years in a randomised, placebo-controlled field trial involving 109,000 schoolchildren in Santiago, Chile. Increasing the interval between doses to twenty-one days did not enhance protection. Significantly less protection followed administration of vaccine in gelatin capsules with sodium bicarbonate. Ty21a provides the same level of protection as the heat/phenol-inactivated whole cell parenteral vaccine but differs in not causing adverse reactions. Ty21a may now be regarded as a practical public health tool.
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D002648:Child; D002677:Chile; D002986:Clinical Trials as Topic; D006801:Humans; D007115:Immunization Schedule; D011897:Random Allocation; D012485:Salmonella typhi / Q000276:immunology; D013608:Tablets, Enteric-Coated; D014435:Typhoid Fever / Q000453:epidemiology / Q000517:prevention & control; D014436:Typhoid-Paratyphoid Vaccines / Q000008:administration & dosage*; D014613:Vaccines, Attenuated
chemical_list: D013608:Tablets, Enteric-Coated; D014436:Typhoid-Paratyphoid Vaccines; D014613:Vaccines, Attenuated