• Jeanne Dieleman, Silvana Romio, Kari Johansen, Daniel Weibel, Jan Bonhoeffer, Miriam Sturkenboom, and VAESCO-GBS Case-Control Study Group.
• Department of Medical Informatics, Erasmus University Medical Center, Rotterdam, Netherlands.
• BMJ. 2011 Jan 1;343:d3908.

ObjectiveTo assess the association between pandemic influenza A (H1N1) 2009 vaccine and Guillain-Barré syndrome.DesignCase-control study.SettingFive European countries.Participants104 patients with Guillain-Barré syndrome and its variant Miller-Fisher syndrome matched to one or more controls. Case status was classified according to the Brighton Collaboration definition. Controls were matched to cases on age, sex, index date, and country.Main Outcome MeasuresRelative risk estimate for Guillain-Barré syndrome after pandemic influenza vaccine.ResultsCase recruitment and vaccine coverage varied considerably between countries; the most common vaccines used were adjuvanted (Pandemrix and Focetria). The unadjusted pooled risk estimate for all countries was 2.8 (95% confidence interval 1.3 to 6.0). After adjustment for influenza-like illness/upper respiratory tract infection and seasonal influenza vaccination, receipt of pandemic influenza vaccine was not associated with an increased risk of Guillain-Barré syndrome (adjusted odds ratio 1.0, 0.3 to 2.7). The 95% confidence interval shows that the absolute effect of vaccination could range from one avoided case of Guillain-Barré syndrome up to three excess cases within six weeks after vaccination in one million people.ConclusionsThe 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. When assessing the association between pandemic influenza vaccines and Guillain-Barré syndrome it is important to account for the effects of influenza-like illness/upper respiratory tract infection, seasonal influenza vaccination, and calendar time.

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