Background: Before the widespread use of rotavirus vaccines, rotavirus was a leading cause of gastroenteritis among children. Navajo and White Mountain Apache children suffer a disproportionate burden of severe rotavirus disease compared with the general U.S. population.
Methods: We enrolled Navajo and White Mountain Apache infants in a multicenter, double-blind, placebo-controlled trial of pentavalent human-bovine reassortant rotavirus vaccine (PRV). Subjects received 3 doses of vaccine or placebo at 4 to 10 week intervals, with the first dose given between 6 and 12 weeks of age. Gastroenteritis episodes were identified by active surveillance. Disease severity was determined by a standardized scoring system.
Results: There were 509 and 494 randomized children who received vaccine and placebo, respectively. Among placebo recipients, the incidence of rotavirus gastroenteritis was 34.2 episodes/100 child-years (95% confidence interval [95% CI]: 25.8-38.9) versus 8.1 episodes/100 child-years (95% CI: 5.4-12.5) in the vaccine group. The percentage of rotavirus episodes caused by serotypes G1, G2, and G3 was 72.3%, 23.4%, and 2.1%, respectively. There were no severe rotavirus episodes among vaccinees and 4 among placebo recipients. PRV was 77.1% (95% CI: 59.7-87.6), 89.5% (95% CI: 65.9-97.9), and 82.9% (95% CI: 61.1-93.6) effective against G1-G4 rotavirus disease, severe and moderate rotavirus disease combined, and outpatient visits for rotavirus disease, respectively. The risk of adverse events was similar for the vaccine and placebo groups.
Conclusions: PRV was highly effective in preventing rotavirus disease and related health care utilization in these American Indian infants. Vaccine efficacy and immunogenicity were similar to the overall study population enrolled in the multicenter trial.