Merck-Glaxo Rotavirus Vaccines Have Slight Risk to Bowel

Vaccines by Merck & Co. and GlaxoSmithKline Plc used to prevent severe diarrhea in infants may carry a slight risk of bowel blockage, two U.S. studies found. The findings weren’t serious enough to change recommendations for the vaccines’ use, researchers said.

Cases of intussusception, a bowel disorder that may require surgery, were found in 1.5 of 100,000 recipients of Merck’s RotaTeq vaccine in a Food and Drug Administration study. A separate study by the Centers for Disease Control and Prevention found five cases of intussusception of 100,000 infants given Glaxo’s Rotarix. Both studies were released online today in the New England Journal of Medicine.

A 1999 withdrawal of Wyeth’s RotaShield, the first licensed rotavirus vaccine due to the product’s ties to intussusception, prompted U.S. health officials to be alert for the effect in vaccines from Merck and Glaxo. Today’s findings are similar to those seen in studies conducted outside the U.S. and suggest the benefits of the vaccines outweigh the risk, the CDC said.

“The CDC continues to recommend that all infants get the vaccine,” Frank DeStefano, director of the agency’s immunization safety office said in a phone interview.

RotaTeq and Rotarix are commonly given to infants to prevent rotavirus disease, which causes half a million deaths globally each year in children younger than 5, according to the CDC. Since the first vaccine was introduced for U.S. infants in 2006, it has reduced rotavirus-related hospitalizations by as many as 50,000 a year, DeStefano said.

$601 Million

Whitehouse Station, New Jersey-based Merck’s RotaTeq, approved in the U.S. in 2006, generated $601 million in 2012. Rotarix, approved in the U.S. in 2008, produced 360 pounds ($571 million) for London-based Glaxo in 2012.

Merck fell less than 1 percent to close at $53 in New York. Glaxo gained less than 1 percent to close at 1,591.50 pence in London.

The CDC study, though it identified a risk with Glaxo’s Rotarix, found no increased risk with Merck’s RotaTeq. The FDA study, though it found a risk associated with RotaTeq, said its analysis showed only a “potential risk” with Rotarix. That study didn’t have enough cases to determine if the risk was significant, researchers said.

Both research teams said their findings were consistent with studies conducted in other countries, including Mexico, Brazil and Australia. The CDC said an Australian study, like the FDA, found increased risk with the RotaTeq vaccine. The difference may be due to several factors, including uncontrolled confounding and methodological differences, the CDC said in its paper.

Watching for Symptoms

“In the case of RotaTeq, there is 1/10th of the risk of RotaShield,” Katherine Yih, researcher at the Harvard Pilgrim Health Care Institute and lead author of the FDA study, said in a phone interview. “It’s not zero, but it’s not too much to worry about.”

Yih advised parents to watch for symptoms of intussusception in the week after their child received the vaccination. Symptoms include vomiting, abdominal swelling, and lethargy.

“The benefits and risks of Rotarix are well documented from pre-licensure clinical efficacy and safety studies enrolling more than 100,000 participants worldwide,” Glaxo spokeswoman Mary Anne Rhyne in an e-mail. “GSK shares the position of the CDC that these additional safety-monitoring data re-affirm the positive benefit-risk profile of Rotarix.”

Michelle Goveia, medical director of Merck Vaccines, said the company values “the important role that rotavirus vaccines play in public health and will continue to monitor the post-licensure experience with RotaTeq.”

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