Rotavirus Vaccine Tied to Short-Term Risk for Intussusception

June 17, 2011 — The monovalent rotavirus vaccine (RV1; Rotarix,
GlaxoSmithKline) carries a short-term risk for bowel intussusception in
roughly 1 of every 51,000 to 68,000 vaccinated infants, a new study
indicates. However, the benefits of the vaccine far outweigh the risks,
the study team emphasizes.
The study appears in the June 16 issue of the New England Journal of Medicine.
In 1999, a rotavirus vaccine (RotaShield, Wyeth
Laboratories) was withdrawn from the US market after postlicensure
surveillance showed it caused intussusception in 1 of every 10,000
infant recipients.
This prompted Manish M. Patel, MD, from the Centers for Disease
Control and Prevention in Atlanta, Georgia, and colleagues to assess the
association of the new monovalent RV1 vaccine with intussusception in
Brazil and Mexico. Brazil added RV1 to their national childhood
immunization programs in March 2006, and Mexico followed in May 2007.
A total of 615 infants with intussusception (285 in Mexico and 330 in
Brazil) and 2050 control infants (739 in Mexico and 1311 in Brazil)
were enrolled in the study. Of these, 594 patients with intussusception
(97%) and 2033 control patients (99%) had a history of vaccination.
Among infants from Mexico, there was roughly a 5-fold increased risk
for intussusception 1 to 7 days after the first dose of RV1. Using a
case-series method, the incidence ratio was 5.2 (95% confidence interval
[CI], 3.0 - 9.3). Using a case-control method, the odds ratio was 5.8
(95% CI, 2.6 - 13.0).
Among infants in Brazil, no significant risk for intussusception was
found after the first dose. However, a small but significantly increased
risk was seen 1 to 7 days after the second dose in both the case-series
analysis (incidence ratio, 2.6; 95% CI, 1.3 - 5.2) and the case-control
series (odds ratio, 1.9; 95% CI, 1.1 - 3.4).
Benefits Clearly Outweigh Risks

The authors point out that the first week after dosing corresponds to
the period of peak intestinal virus replication, during which a local
inflammatory response in the lymphatic tissue or intestines may occur,
"a response that has been implicated in the pathogenesis of
intussusception."
They emphasize, however, that the increased risks uncovered from
their analysis translated into an annual excess of 96 hospitalizations
for intussusception, and 5 deaths in the 2 countries combined.
These figures, they say, "are outweighed by the real-world benefits
of RV1 vaccination, which has annually prevented more than 80,000
hospitalizations and 1300 deaths in Mexico and Brazil."
They further point out that these "emerging" data on RV1 have been
reviewed by the World Health Organization, as well as by regulatory
agencies and immunization advisory committees in Brazil, Mexico, and the
United States. All of these organizations have unanimously favored
continuing the recommendation that rotavirus vaccination be administered
to infants to prevent severe and potentially fatal rotavirus disease.
The study was supported in part by the
Global Alliance for Vaccines and Immunization and the US Department of
Health and Human Services. The authors have disclosed no relevant
financial relationships.