Twenty-eight cases of intussusception have been reported to the FDA following immunization with Merck's RotaTeq; however, the agency said it is not certain the incidents are due to the vaccine itself. All of the infants affected survived, and 16 required surgery to fix the condition, which causes the intestines to become blocked or twisted. CDC said it has not changed its recommendation that infants receive the vaccine as part of their regular immunization schedule but is monitoring the product carefully. In 1999, Wyeth's rotavirus vaccine was pulled from the market following its link to intussusception. Merck said it has updated RotaTeq's prescribing information to include the 28 cases reported.