N 1999, THE RHESUS TETRAVALENT rotavirus vaccine (RRV, Rotashield, Wyeth) was withdrawn from the US market due to a significantly increased risk of intussusception following vaccination. The largest increased risk (Ͼ30-fold) of intussusception was observed during the 3 to 7 days following the first dose of the vaccine. [1][2][3] Since then, 2 vaccines to prevent rotavirus infection have been licensed for use in the United States: a pentavalent rotavirus vaccine (RV5, RotaTeq, Merck) in 2006 and a monovalent rotavirus vaccine (RV1, Rotarix, GlaxoSmithKline Biologicals) in 2008. 4,5 The pentavalent rotavirus vaccine is a 3-dose series that, according to the Advisory Committee on Immunization Practices, should be given at ages 2, 4, and 6 months; RV1 is a 2-dose series to be