Vaccination has been associated with a decline in rotavirus-associated illness, but concern about intussusception remains. In this CDC report, the monovalent rotavirus vaccine was associated with a slight increase in intussusception risk, as compared with the pentavalent vaccine. The first licensed rotavirus vaccine (RotaShield) was withdrawn from the U.S. market in 1999 because of an increased risk of intussusception. 1 Subsequently, two rotavirus vaccines have been licensed in the United States: RotaTeq (a pentavalent rotavirus vaccine) in 2006 and Rotarix (a monovalent rotavirus vaccine) in 2008. 2 , 3 The two vaccines underwent prelicensure clinical trials involving 60,000 to 70,000 infants each, in which no increased risk of intussusception was identified. 4 , 5 Postlicensure monitoring in the Vaccine Safety Datalink (VSD) project has not found an increase in the risk of intussusception after pentavalent rotavirus vaccination. 6 , 7 At the time of the . . .