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H1N1, Seasonal Flu Vaccines From 2009 to 2010 Were Safe

Seasonality likely contributed to Bell's palsy signal following monovalent inactivated vaccine

FRIDAY, July 8 (HealthDay News) -- The pandemic H1N1 influenza and seasonal influenza vaccines administered during the 2009 to 2010 season had no associated major safety problems, according to a study published online July 5 in the American Journal of Preventive Medicine.

Grace M. Lee, M.D., M.P.H., from the Harvard Pilgrim Health Care Institute and Harvard Medical School in Boston, and colleagues examined the safety of H1N1 and seasonal influenza vaccines during the 2009 to 2010 season. Data were collected from the Vaccine Safety Datalink (VSD) project which is a collaboration of eight U.S. medical care organizations, and includes approximately 9.2 million children and adults. Electronic data on vaccines and prespecified adverse events were analyzed on a weekly basis from September 2009 to April 2010. Temporal clusters were identified and time-varying confounders controlled for.

The investigators found that as of May 1, 2010, the following vaccine doses were administered in VSD: 1,345,663 H1N1 monovalent inactivated vaccines (MIV), 267,715 live attenuated monovalent vaccines, 2,741,150 seasonal trivalent inactivated vaccines, and 157,838 live attenuated influenza vaccines. Analyses for Guillain-Barré syndrome, most other neurologic outcomes, and allergic and cardiac effects, did not show significant associations with vaccination. A statistical signal was observed for MIV for Bell's palsy in adults age 25 years or older. Based on further analyses, no significant temporal cluster was identified. After adjusting for seasonality, case-centered logistic regression showed Bell's palsy had an odds ratio of 1.26 (95 percent confidence interval, 0.97 to 1.63).

"No major safety problems following H1N1 or seasonal influenza vaccines were detected in the 2009 to 2010 season in weekly sequential analyses. Seasonality likely contributed to the Bell's palsy signal following MIV," the authors write.

Two authors disclosed financial ties to the pharmaceutical industry. The study was supported by a subcontract with America's Health Insurance Plans.

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