CDC: Benefits of Vaccination Still Far Exceed Risks
By Salynn Boyles
WebMD Health News
Reviewed by Louise Chang, MD
June 15, 2011 -- A vaccine that prevents the most common cause of severe diarrhea and dehydration in babies was associated with a potentially life-threatening bowel disorder in a large study from Mexico and Brazil, but the risk was small.
Investigators with the CDC and health agencies in Latin America concluded that between 1 in 51,000 and 1 in 68,000 vaccinated babies given the rotavirus vaccine Rotarix, manufactured by GlaxoSmithKline, could be expected to develop intussusception, a condition in which part of the intestine slides into another part of the intestine, like parts of a telescope.
Another rotavirus vaccine, Wyeth Lab's RotaShield, was withdrawn from the market in the U.S. in 1999 less than a year after its introduction. At the time, the FDA determined that the vaccine caused intussusception in 1 in 10,000 babies who got it.
Bowel Risk Not Limited to RotaShield
The new study confirms that the bowel obstruction risk was not limited to the withdrawn vaccine, but it also makes it clear that the benefits of vaccination far exceed the risks, epidemiologist Umesh D. Parashar, MD, of the CDC's National Center for Immunization and Respiratory Diseases, tells WebMD.
According to health surveillance data from Mexico and Brazil, about 80,000 hospitalizations and 1,300 deaths are prevented in the two countries every year by vaccinating babies against rotavirus.
If the rotavirus vaccine-associated risk in the United States is the same as in Latin America, Parashar says vaccination is probably responsible for 50 to 60 cases of intussusception each year nationwide, while preventing 40,000 to 50,000 rotavirus-related hospitalizations.
"The risk with the vaccines we have now appears to be five to 10 times lower than that seen with RotaShield," he says. "And the benefits far outweigh the risks both in the United States and elsewhere."
Rotavirus is responsible for more than 500,000 deaths each year, primarily in underdeveloped countries, but it is also a significant cause of childhood illness in more affluent nations.
Before the introduction of the rotavirus vaccine, as many as 70,000 rotavirus hospitalizations and about 60 deaths were reported in the U.S. each year.
Natural Infection May Also Cause Bowel Disorder
Rotarix is one of two rotavirus vaccines licensed for use in the United States.
The other, Merck's RotaTeq, was not used in the Latin American populations included in the newly reported study, but researchers in Australia have reported a small intussusception risk with that vaccine, Stanford University professor of microbiology and immunology Harry Greenberg, MD, notes in an editorial published with the study.
Both appear in the June 16 issue of The New England Journal of Medicine.
"We can infer from these studies that any orally administered live rotavirus vaccines will probably carry some detectable risk of intussusceptions ... and that the risk seems to be small," he writes.
In a news release, Williams notes that vaccination may not actually increase intussusception risk, because it now appears that natural rotavirus infection can also cause the bowel obstruction.
Children's Hospital of Philadelphia rotavirus vaccine researcher Paul A. Offit, MD, agrees.
Offit, who is a co-developer of the RotaTeq vaccine, tells WebMD that vaccination may prove to be associated with a lower risk for intussusception than natural rotavirus infection.
"Decisions about any medical treatment come down to whether the benefits outweigh the risks," Offit says. "I would argue that in this case the choice is an easy one, because rotavirus is very common and intussusception is quite rare. Before the rotavirus vaccine was available, between 55,000 and 70,000 children [in the U.S.] were hospitalized every year from rotavirus and around 60 children died."
In a statement provided to WebMD, GlaxoSmithKline affirms its confidence in the safety of Rotarix, noting that the company continues to monitor its safety worldwide.
"Due to the efficacy demonstrated by the vaccine in helping to protect against rotavirus gastroenteritis, the expected benefit from rotavirus vaccination exceeds the risk related to intussusception," the statement reads.