Abstract

Background Peak incidence of rotavirus gastroenteritis is seen in infants between 6 and 24 months of age. We therefore aimed to assess the 2-year efficacy and safety of an oral live attenuated human rotavirus vaccine for prevention of severe gastroenteritis in infants. Methods 15183 healthy infants aged 6-13 weeks from ten Latin American countries randomly assigned in a 1 to 1 ratio to receive two oral doses of RIX4414 or placebo at about 2 and 4 months of age in a double-blind, placebo-controlled phase III study were followed up until about 2 years of age. Primary endpoint was vaccine efficacy from 2 weeks after dose two until 1 year of age. Treatment allocation was concealed from investigators and parents of participating infants. Efficacy follow-up for gastroenteritis episodes was undertaken from 2 weeks after dose two until about 2 years of age. Analysis was according to protocol. This study is registered with ClinicalTrials.gov, number NCT00140673 (eTrack444563-023). Findings 897 infants were excluded from the according-to-protocol analysis. Fewer cases (p0.0001) of severe rotavirus gastroenteritis were recorded for the combined 2-year period in the RIX4414 group (32 [0.4%] of 7205; 95% CI 0 . 3-0.6) than in the placebo group (161 [2.3%] of 7081; 1 . 9-2.6), resulting in a vaccine efficacy of 80.5% (71.3-87. 1) to 82.1% (64.6-91.9) against wild-type G1, 77.5% (64.7-86.2) against pooled non-G1 strains, and 80.5% (67.9-88 . 8) against pooled non-G1 P[81 strains. Vaccine efficacy for hospital admission for rotavirus gastroenteritis was 83. 0% (73.1-89.7) and for admission for diarrhoea of any cause was 39.3% (29.1-48 . 1). No cases of intussusception were reported during the second year of follow-up. Interpretation Two doses of RIX4414 were effective against severe rotavirus gastroenteritis during the first 2 years of life in a Latin American setting. Inclusion of RIX4414 in routine paediatric immunisations should reduce the burden of rotavirus gastroenteritis worldwide.