The Food and Drug Administration on Tuesday issued a public health notification to alert care providers and consumers that 28 infants reportedly suffered a life-threatening condition last year after they received Merck’s rotavirus vaccine known as RotaTeq.

The vaccine was approved by the FDA in Feb 2006 for use in infants to prevent common and highly contagious rotavirus infections, which cause gastroenteritis, leading to diarrhea, vomiting, fever, and dehydration.

The life-threatening condition known as intussusception occurs in infants naturally or can be implicated by administration of this vaccine, leading to twisting of intestines. When it occurs, one portion of the intestine tangles with a nearby portion, causing the intestinal obstruction, the FDA says.

The federal agency says it does not know how many out of these 28 cases were caused by the rotavirus vaccine. Neither does it know the total number of the infants who suffered the condition last year.   Adverse effects of a vaccine are not always reported to the FDA.

The FDA asks the public to be aware of the risk of the potentially life-threatening condition as a previous rotavirus vaccine known as RotaShield made by Wyeth used for the same indication was found to raise the risk of intussusception in infants and was later pulled out of the market in 1999.

These 28 cases have been reported in the U.S. infants who received RotaTeq since licensure of the vaccine on Feb. 3, 2006 until January 31, 2007.   All the cases occurred 0 to 73 days after dose 1, dose 2 and dose 3 with nearly 50 percent occurring during the first 21 days after vaccination.

Among these 28 cases, sixteen infants were admitted to hospital and underwent surgery on their intestine. All others had reduction of the intussusception by contrast or air enema, according to the FDA.    But no death resulting from the condition was reported.

According to the FDA, unpublished data from the Centers for Disease Control and Prevention show 18 to 43 cases of intussusception per 100,000 per year (the background rate) are expected to occur naturally in an unvaccinated population of children aged 6 to 35 months. This means, according to news reports, that about 500 natural cases were expected for last year.

"It looks like this is the natural background rate that we are seeing," Houston Chronicle quoted Dr. Michelle Goveia, medical director for pediatric medical affairs at the vaccine's manufacturer, Merck & Co. Inc. as saying.

But the number of reported cases is so low that many cases last year might be unreported.   The FDA indicates that the real number of cases was likely underreported and the possibility cannot be excluded that use of the rotavirus vaccine may increase the risk of intussusception.

The FDA says the notification is "to encourage the reporting of any additional cases of intussusception that may have occurred or occur in the future after administration of RotaTeq and to remind people that intussusception is a potential complication of RotaTeq."  

"Parents should contact their child’s doctor immediately if the child has stomach pain, vomiting, diarrhea, blood in their stool or change in their bowel movements, as these may be signs of intussusception.   It is important to contact the child’s doctor if there are any questions or if the child has any of these symptoms at any time after vaccination, even if it has been several weeks since the last vaccine dose.," the FDA states in its notice.

Any information on adverse effects can help the agency to assess the  safety of the vaccine. To report a case, parents may call 1-800-822-7967 for a copy of the vaccine reporting form or report directly on line to www.vaers.hhs.gov.

Rotavirus is the most common cause of severe diarrhea among children resulting in hospitalization of 55,000 children each year in the U.S., according to the CDC.   For persons with healthy immune systems, rotavirus gastroenteritis lasts only a few days and causes no obvious harm.   The mortality rate is extremely low, 20 to 60 deaths a year.