A large study of the French national health data system failed to identify an association between seasonal influenza immunization and risk for Guillain-Barre ́ syndrome (GBS), but researchers did find an increased risk for GBS after a respiratory tract or gastrointestinal infection. Findings from this study were published in Neurology.
The study identified patients with GBS in the French national hospital discharge database who were hospitalized between 2010 and 2014. A self-controlled case series was used to assess the association between GBS and immunization for seasonal influenza. The risk period began 1 day after vaccination and lasted until 42 days after vaccination (D1 and D42, respectively). Researchers compared the incidence of GBS during this risk period with the incidence rate during the control period (D43-March 31). Adjustments for seasonality and infections were performed in the estimation of the incidence rate ratios (IRRs).
A total of 3523 GBS cases occurred in metropolitan France during the 2010/2011 to 2013/2014 influenza vaccination seasons. Fifteen percent (n=527) of patients who developed GBS during these periods had received the influenza vaccine, with 140 patients developing GBS during the 42-day period after immunization. In the crude analysis, the risk of developing GBS was not significantly increased during the postvaccination 42-day period (IRR, 1.02; 95% CI, 0.83-1.25; P =.85).
After adjustment for calendar months and the incidence of acute gastrointestinal and respiratory tract infections, there was still no significant increase in the risk of developing GBS after vaccination (IRR, 1.10; 95% CI, 0.89-1.37; P =.38). The risk for GBS was significantly higher after an acute respiratory tract infection (IRR, 3.89; 95% CI, 3.52-4.30; P <.0001) or gastrointestinal infection (IRR, 3.64; 95% CI, 3.01-4.40; P <.0001).
A limitation of the study included the researchers’ difficulty in identifying all infections and influenza infections in this cohort.
The investigators concluded that despite no risk found for GBS after influenza vaccination, routine “new pharmacoepidemiology studies on influenza vaccine remain justified because the composition of the vaccine varies each year.”
Grave C, Boucheron P, Rudant J, et al. Seasonal influenza vaccine and Guillain-Barré syndrome: a self-controlled case series study [published online February 25, 2020]. Neurology. doi:10.1212/WNL.0000000000009180