Heterogeneity of Rotavirus Vaccine Efficacy Among Infants in Developing Countries.

BACKGROUND:Rotavirus is the leading cause of severe diarrhea worldwide in young children. Although rotavirus vaccine efficacy is high in developed countries, efficacy is lower in developing countries. Here, we investigated heterogeneity of rotavirus vaccine efficacy by infant characteristics in developing countries. METHODS:An exploratory, post hoc analysis was conducted using randomized controlled trial data of the pentavalent rotavirus vaccine (RV5) conducted in Africa and Asia (NCT00362648). Infants received either 3 doses of vaccine/placebo and were followed for up to 2 years. Within subgroups, vaccine efficacies and 95% confidence intervals (CIs) against rotavirus gastroenteritis (RVGE) were estimated using Poisson regression. We assessed heterogeneity of efficacy by age at first dose, gender, breastfeeding status and nutrition status. RESULTS:African children receiving the first dose at <8 weeks had lower efficacy (23.7%; 95% CI: -8.2%-46.3%) than those vaccinated at ≥8 weeks (59.1%; 95% CI: 34.0%-74.6%). Marginally statistically significant differences were observed by age at first dose, gender and underweight status in Ghana and gender in Asian countries. CONCLUSIONS:Heterogeneity of efficacy was observed for age at first dose in African countries. This was an exploratory analysis; additional studies are needed to validate these results.