Field Trials of Attenuated Salmonella typhi Live Oral Vaccine TY21A in Liquid andEnteric-Coated Capsule Formulations in Santiago, Chile

摘要

In a randomized, double-blind, controlled field trial in Santiago, Chile, 81,621school-children, 5-19 years of age, received three doses, within one week, of attenuated Salmonella typhi oral vaccine Ty21a in enteric-coated capsules or in a new liquid suspension, or placebo. Over 36 months of surveillance, the liquid formulation (76.9% vaccine efficacy) was markedly superior to enteric-coated capsules (33.2% vaccine efficacy) (p=0.0000077). The liquid formulation protected young children (5-9 years old) (vaccine efficacy 82.3%) as well as older children > or = 10 years) (69.3% vaccine efficacy), while the capsules significantly protected only older children. The liquid suspension was practical to prepare by mixing lyophilized vaccine with buffer in water and was easily administered, even to the youngest children. It was concluded that the liquid formulation of Ty21a is preferable to enteric-coated capsules. (TTL)