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Comparison of enteric-coated capsules and liquid formulation of Ty21a typhoid vaccine in randomised controlled field
M M Levine1, C Ferreccio, S Cryz
1Center for Vaccine Development, University of Maryland School of Medicine, Baltimore 21201.
Insights
A new liquid Salmonella typhi oral vaccine (Ty21a) showed superior efficacy (76.9%) compared to enteric-coated capsules (33.2%) in a large trial. This liquid formulation offers better protection, especially for younger children.
Area of Science:
- * Infectious Diseases
- * Vaccinology
- * Public Health
Background:
- * Typhoid fever remains a significant global health concern, necessitating effective vaccination strategies.
- * Oral vaccines like Ty21a offer an alternative to injectable typhoid vaccines.
- * Previous formulations of Ty21a utilized enteric-coated capsules, with varying efficacy.
Purpose of the Study:
- * To compare the efficacy and safety of a novel liquid suspension formulation of the attenuated Salmonella typhi oral vaccine Ty21a against its enteric-coated capsule form.
- * To evaluate the vaccine's effectiveness across different age groups within the pediatric population.
Main Methods:
- * A randomized, double-blind, placebo-controlled field trial involving 81,621 schoolchildren aged 5-19 years in Santiago, Chile.
- * Participants received three doses of either the liquid Ty21a suspension, enteric-coated Ty21a capsules, or a placebo within one week.
- * Surveillance for typhoid fever was conducted over a 36-month period.
Main Results:
- * The liquid Ty21a formulation demonstrated significantly higher vaccine efficacy (76.9%) compared to the enteric-coated capsules (33.2%).
- * The liquid formulation provided robust protection in both younger children (5-9 years, 82.3% efficacy) and older children (69.3% efficacy).
- * Enteric-coated capsules only showed significant protection in older children.
Conclusions:
- * The liquid suspension formulation of Ty21a is superior to enteric-coated capsules for typhoid fever prevention in schoolchildren.
- * The ease of preparation and administration of the liquid form makes it a practical option, particularly for younger children.
- * This enhanced liquid formulation represents a significant advancement in oral typhoid vaccination.
Abstract:
In a randomised, double-blind, controlled field trial in Santiago, Chile, 81,621 schoolchildren aged 5-19 years received three doses, within a 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 significantly superior to the enteric-coated capsules (33.2% vaccine efficacy). The liquid formulation protected young children (5-9 years) (efficacy 82.3%) as well as older children (efficacy 69.3%), whereas the capsules significantly protected only older children. The liquid suspension was easy to prepare by mixing lyophilised vaccine with buffer in water and was easily administered, even to the youngest children. Thus, the liquid formulation of Ty21a is preferable to enteric-coated capsules.