(HealthDay News) – The risk of intussusception is still increased after administration of the new rotavirus vaccines, but the risk is lower than that seen with previous vaccines, according to two studies published online Jan. 14 in the New England Journal of Medicine. The studies were published ahead-of-print to coincide with the sixth annual Sentinel Initiative Public Workshop at the Brookings Institution, held on Jan. 14 in Washington, DC.

W. Katherine Yih, PhD, MPH, from Harvard Medical School and the Harvard Pilgrim Health Care Institute in Boston, and colleagues examined the risk of intussusception after vaccination with pentavalent RotaTeq (RV5) and monovalent Rotarix (RV1) for infants aged 5–36.9 weeks. The researchers observed a significant elevation in the number of excess cases of intussusception per 100,000 recipients of the first dose of RV5 in primary analysis (attributable risk, 1.5 for the 21-day risk window) and secondary analysis (attributable risk, 1.2). For RV1, the results of the primary analysis were not significant, but a significantly increased risk was seen after dose two in secondary analysis.

Eric S. Weintraub, MPH, from the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues examined the risk of intussusception after monovalent rotavirus vaccination among infants aged 4–34 weeks in the United States. The researchers identified six cases of intussusception within seven days of administration of either dose of vaccine. Compared with an expected 0.72 cases, there was a significantly increased relative risk of 8.4. For the pentavalent vaccine, the relative risk was nonsignificant at 1.1. The risk attributable to the monovalent rotavirus vaccine was estimated at 5.3 per 100,000 infants vaccinated.

“We observed a significant increase in the rate of intussusception after vaccination, a risk that must be weighed against the benefits of preventing rotavirus-associated illness,” Weintraub and colleagues write.

One author from the Yih study disclosed being employed by and holding stock in Aetna.

Full Text – Yih
Full Text – Weintraub
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