H1N1 2009 Vaccine Not Tied to Guillain Barré Syndrome Risk

Adjuvanted pandemic influenza A 2009 vaccine does not increase Guillain Barré syndrome risk

THURSDAY, July 14 (HealthDay News) -- The adjuvanted pandemic influenza A (H1N1) 2009 vaccine is not associated with an increased risk of Guillain-Barré syndrome, according to a study published July 12 in the BMJ.

Jeanne Dieleman, Ph.D., from Erasmus University Medical Center in Rotterdam, Netherlands, and colleagues investigated the association between H1N1 2009 vaccine and Guillain-Barré syndrome. A total of 104 patients with Guillain-Barré syndrome and its variant, Miller-Fisher syndrome, were selected from five European countries and matched to one or more controls for age, gender, index date, and country. Brighton collaboration definition levels 1 to 3 were used to classify the case status. Relative risk estimate for Guillain-Barré syndrome after pandemic influenza vaccine was the main outcome of the study.

The investigators found that, though case recruitment and vaccine coverage varied considerably between countries, adjuvanted vaccines (Pandemrix and Focetria) were the most commonly used. An unadjusted pool risk estimate of 2.8 was noted for all countries. The receipt of H1N1 vaccine was not associated with an increased risk of Guillain-Barré syndrome, after adjusting for influenza-like illness/upper respiratory tract infection and seasonal influenza vaccination (adjusted odds ratio, 1.0, 95 percent confidence interval, 0.3 to 2.7). Within six weeks after vaccination, its absolute effect ranged from one avoided Guillain-Barré syndrome case to three excess cases in one million people.

"The risk of occurrence of Guillain-Barré syndrome is not increased after pandemic influenza vaccine, although the upper limit does not exclude a potential increase in risk up to 2.7-fold or three excess cases per one million vaccinated people," the authors write.

Several authors disclosed financial ties with the pharmaceutical industry.

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