Rotavirus gastroenteritis results in 37% of deaths caused by diarrhoea worldwide, but the cost and supply of available vaccines prevents their use in some countries, such as sub-Saharan Africa. A cheaper, live, oral bovine rotavirus pentavalent vaccine (BRV-PV) has now been developed and tested in a randomized, placebo-controlled trial in Niger. Healthy infants received three doses of either BRV-PV or placebo at 6, 10, and 14 weeks of age; the primary end point was the efficacy of vaccine versus placebo against a first episode of severe rotavirus gastroenteritis. Of 3,508 infants included in the per-protocol analysis, there were 31 cases of rotavirus gastroenteritis in the vaccine group and 81 cases in the placebo group. Thus, BRV-PV had an efficacy of 66.7% against rotavirus gastroenteritis. No significant between-group differences in the risk of adverse events were found.