September 23, 2010 — The US Food and Drug Administration (FDA) has revised the label of the rotavirus vaccine Rotarix (GlaxoSmithKline) to warn of a small increased risk for intussusception that was reported in a Mexican study, the agency announced yesterday.
A potentially life-threatening condition, intussusception occurs when 1 portion of the intestine telescopes into another. This anomaly, which can develop in the absence of vaccination, may lead to internal bleeding, an intestinal hole, and abdominal infection.
The annual rate of spontaneous intussusception — and subsequent hospitalization — is roughly 34 in 100,000 healthy young infants and children, the FDA stated.
Symptoms, which usually develop suddenly, include fussiness, frequent vomiting, diarrhea or stools containing blood or mucus, and severe belly pain, cramping, and swelling.
Preliminary results from a postmarketing study of Rotarix in Mexico suggest that there is an increased risk for intussusception in the 31 days after the first dose, with a relative risk of 1.8, according to the agency. Most cases occurred during the first 7 days after the first dose.
Extrapolated to the United States, these results would represent up to 4 additional hospitalizations due to intussusception per 100,000 infants within 31 days of the first Rotarix dose. The agency noted that the annual background rate of intussusception in Mexico — between 60 and 90 per 100,000 children — is higher than that in the United States.
The FDA said it would review the final results from the Mexican study when they become available in 2011. It noted that GlaxoSmithKline is conducting a postmarketing study of Rotarix and intussusception in the United States.
In 1999, the rotavirus vaccine RotaShield was withdrawn from the market after studies suggested an elevated risk for intussusception on the order of 9 additional cases per 100,000 infants.
No increased risk for this bowel condition emerged in clinical trials for both Rotarix and another rotavirus vaccine, RotaTeq (Merck), but the agency nevertheless has monitored the 2 vaccines for this potential problem.
The postmarketing study in Mexico did not examine RotaTeq, and it is not undergoing a label revision.
The FDA said it has uncovered no evidence of an increased risk for intussusception with RotaTeq, but it will continue to study the issue.
More information about yesterday's FDA announcement is available on the agency's Web site.
The FDA and the US Centers for Disease Control and Prevention encourage clinicians to report intussusception or any adverse event after vaccination to the Vaccine Adverse Event Reporting System.
Disclosure: Robert L. Lowes has disclosed no relevant financial relationships.