(RxWiki News) Vaccines have made a tremendous difference in reducing the risk of disease in the US. Yet the benefits of vaccines do not mean there are no risks to them.
A recent pair of studies found an increased risk of intussusception with the current rotavirus vaccines. Intussusception is a serious medical condition in which part of the bowel slides into another part in a sort of "telescope" movement.
Rotavirus is a gastrointestinal illness that causes severe diarrhea and potentially dehydration.
In 1999, a previous rotavirus vaccine called RotaShield was voluntarily recalled because of an increased risk of one to two cases of intussusception per 10,000 doses.
"Discuss vaccinations with your child's pediatrician."
One study was led by Eric Weintraub, MPH, of the US Centers for Disease Control and Prevention, and the other by W. Katherine Yih, PhD, MPH, of Harvard Medical School.
Both studies looked at the risk of intussusception following rotavirus vaccination with different brands of vaccines.
In the study by Weintraub, the researchers reviewed the medical records for babies, aged 1 to 8 months, who received the vaccine between April 2008 and March 2013.
During this time, 115,908 first doses of the Rotarix vaccine and 92,047 second doses of Rotarix were administered to the children — all part of six health care organizations monitored in the Vaccine Safety Datalink program.
Within the first week after receiving the Rotarix vaccine, six babies experienced intussusception, which is more than the one case that would be expected in a similarly sized ordinary population.
The researchers therefore calculated that the increased risk of intussusception among children was an extra 5.3 cases per 100,000 babies who received the Rotarix vaccine, above what would normally be seen without the vaccine.
Meanwhile, out of the 1.3 million doses of RotaTeq administered, eight children experienced intussusception compared to the seven who would be expected independent of vaccination.
This increased risk could have been due to chance, so the researchers concluded that RotaTeq did not appear linked to an increased risk of intussusception.
The risk of intussusception with the monovalent Rotarix was about nine times higher than the risk with the pentavalent RotaTeq vaccine.
The study by Yih involved children aged 1 month to 9 months old who were enrolled in one of three US health plans and received the vaccine between 2004 and mid-2011.
Out of 1.3 million total doses administered of RotaTeq (including 507,874 first doses), the researchers found a risk of 1.5 additional cases of intussusception per 100,000 children receiving the first dose of the vaccine.
This finding translated to a 10 percent higher risk in the week after vaccination with a first dose and a 20 to 50 percent increased risk in the three weeks after vaccination. No increased risks were seen for second or third doses of the vaccine.
Out of 103,098 total doses of Rotarix (including 53,638 first doses), the researchers did not find an increased risk after the first dose but did find a very slight increased risk after the second dose.
However, the much smaller number of doses analyzed for Rotarix limited how much the researchers could learn about the risks of this vaccine.
The authors of both studies concluded that the apparent increased risks of intussusception with the rotavirus vaccine should be taken into account along with the benefits of preventing rotavirus.
Both studies were published Tuesday in the New England Journal of Medicine.
The Weintraub study was funded by the CDC.
Two authors have received past grants from Inviragen, another has received a grant from GlaxoSmithKline, and a fourth has received past grants from GlaxoSmithKline, Merck & Co., Sanofi Pasteur, Pfizer and Novartis. No other authors reported potential conflicts of interest.
The Yih study was funded by the US Food and Drug Administration through the Department of Health and Human Services. One author is an employee and stockholder at Aetna. No other authors reported potential conflicts of interest.