The influenza vaccination can reduce the risk of contracting Guillain-Barré syndrome, contrary to previous evidence.
The study results are in contrast to the findings of other recent studies that have shown a modest increase in risk of Guillain-Barré syndrome (GBS) with the influenza vaccine compared to the influenza virus.
GBS is often preceded by a respiratory or gastrointestinal infection. Previous studies have estimated that the influenza virus increases the risk of GBS by up to 16- to 18-fold, and the influenza vaccination by up to 2-fold. This evidence is often cited by health care workers that are required to receive the vaccination.
The researchers evaluated the risk of GBS following vaccination through simulated models of a woman aged 45 and a man aged 75. In the model, which accounted for age, sex, influenza incidence, and vaccine effectiveness, the excess GBS risk for influenza vaccination vs. no vaccination was −0.36/1 million vaccinations (95% credible interval −1.22% to 0.28%) for the woman and −0.42/1 million vaccinations (95% credible interval, –3.68% to 2.44%) for the man.
The results show a small absolute reduction in GBS risk with vaccination.
The researchers hope that the results will boost confidence in the influenza vaccine and encourage health care professionals to put the risk of GBS with influenza vaccination in greater context.
It is unclear whether seasonal influenza vaccination results in a net increase or decrease in the risk for Guillain-Barré syndrome (GBS). To assess the effect of seasonal influenza vaccination on the absolute risk of acquiring GBS, we used simulation models and published estimates of age- and sex-specific risks for GBS, influenza incidence, and vaccine effectiveness.
For a hypothetical 45-year-old woman and 75-year-old man, excess GBS risk for influenza vaccination versus no vaccination was −0.36/1 million vaccinations (95% credible interval −1.22% to 0.28%) and −0.42/1 million vaccinations (95% credible interval, –3.68% to 2.44%), respectively.