The Food and Drug Administration is telling consumers and doctors to be aware of a serious potential side effect from a
vaccine that protects infants against virus-induced diarrhea, vomiting and fever.
There haven't been any deaths associated with Merck's RotaTeq vaccine, which guards against the highly contagious rotavirus, the FDA said Tuesday after the markets had closed.
However, the agency has received reports of 28 cases of a complication in which an infant's intestine gets blocked or twisted, causing an obstruction. This condition, called intussusception, can occur by itself, and the FDA doesn't know how many of the 28 cases were linked to the vaccine. Sixteen infants required surgery.
"Because vaccine adverse events are not always reported to FDA, there may be additional cases of intussusception following vaccination of which we are unaware at this time," the agency says. The agency has ordered a label revision to reflect the new information and is encouraging consumers to tell it about suspected cases.
Intussusception was the reason why
removed a similar vaccine in 1999 after only one year on the market.
Merck is overseeing a post-marketing survey of 44,000 infants to determine the rate of intussusception, and the federal Centers for Disease Control and Prevention is conducting its own study of 90,000 infants. The FDA said the number of cases at this time is within the range of expected side effects based on the CDC's calculations for unvaccinated children between the ages of 6 weeks to 35 weeks.
Merck's clinical trials found no significant difference in the intestinal obstruction between some 35,000 infants getting the vaccine and another 35,000 getting a placebo. Six vaccine patients and five placebo recipients developed intussusception.
The FDA approved the vaccine 12 months ago. Approximately 3.5 million doses had been distributed through Feb. 1, although some doses haven't been administered, the agency says. Infants receive three doses. A doctor squeezes the liquid vaccine from a tube into an infant's mouth.
The vaccine, which is sold in 34 countries, produced $163 million in sales last year. Applications for its approval have been filed in more than 100 countries.