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Intussusception risk seen with newer rotavirus vaccines.

Two large U.S.-based studies have found the risk of intussusception, a rare type of bowel obstruction in infants, to be elevated after rotavirus vaccination.

Concerns about intussusception risk date back to 1999, when a tetravalent rotavirus vaccine was withdrawn by its manufacturer after being shown to be associated with between one and two excess cases per 10,000 infants vaccinated.

Findings from clinical trials of newer pentavalent and monovalent vaccines, introduced in 2006 and 2008, respectively, showed no such excess intussusception risk.

Data from the first of the new studies show a slight but statistically significant increase in intussusception risk associated with use of Merck's pentavalent vaccine, RV5 (RotaTeq) (N. Engl. J. Med. Jan. 14 [doi:10. 1056/NEJMoa11303164]).

For their research, Katherine Yih, Ph.D., of Harvard Medical School and the Harvard Pilgrim Health Care Institute, Boston, and her associates looked at data from more than 1.2 million doses of RV5. Using data from 507,874 first doses and 1,277,556 total doses of RV5, Dr. Yih's team found an excess risk of 1.5 cases per 100,000 within 21 days after the first dose (95% confidence interval, 0.2-3.2), with no further increases in risk seen after the second or third dose. This represents about 10% of the excess risk seen with the first-generation vaccine.

A separate study assessed intussusception cases recorded within 7 days after a first or second dose of the monovalent vaccine (N. Engl. J. Med. [doi:10.1056/NEJMoal311708]).

The investigators, led by Eric Weintraub, of the Centers for Disease Control and Prevention in Atlanta, found 5.3 excess cases over expected background rates per 100,000 infants vaccinated with two doses. The authors acknowledged that their findings of elevated risk could be due to chance, given the small number of cases seen in the study.

In the same study, Mr. Weintraub and his colleagues found no increase in risk associated with the pentavalent vaccine, for which there were data on 1,301,810 doses. However, they noted, the confidence intervals for this finding were wide.

The data used in Mr. Weintraub and colleagues" study came from the Vaccine Safety Datalink surveillance program run by the CDC.

Mr. Weintraub's study was funded by the CDC. One of Dr. Yih's coauthors disclosed being an employee and stockholder of Aetna, which participates in the Mini-Sentinel program.

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Author:Smith, Jennie
Publication:Family Practice News
Date:Jan 1, 2014
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