Influenza vaccination increases risk of Guillain-Barre syndrome within one month

The study summary includes the following:

• This was a retrospective nationwide population-based case–control study.
• The data collection was done on all patients with first-time hospital-diagnosed GBS in Denmark (2002 and 2016).
• The incident influenza vaccination one month before admission with GBS was the primary outcome measured in the study.
• The authors identified 1295 patients with first-time hospital-diagnosed Guillain–Barré syndrome (GBS) over approximately 14 years and correlated the occurrence of GBS with exposure to influenza vaccination.
• Twenty cases comprising 1.5%, and 119 controls comprising 0.9%, received an influenza vaccination (last month).
• The value of the comorbidity-adjusted odds ratio was 1.9.
• Similar results were on stratified analyses by calendar time, gender and age.
• After influenza vaccination, there was a higher risk of GBS confined largely to 1 month.
• The population-attributable fraction of GBS was 0.4% in Denmark.

To conclude, Influenza vaccination slightly elevates the risk of GBS occurrence within one month. Compared with matched controls, individuals who received influenza vaccination had a slightly elevated risk of GBS occurrence within the first month after vaccination.

The benefit of influenza vaccines and associated morbidity and mortality should be weighed against the small absolute risk of Guillain-Barre syndrome.

Further reading:

Levison, Lotte Sahin, et al. “Guillain–Barré Syndrome Following Influenza Vaccination: A 15‐year Nationwide Population‐based Case–control Study.” European Journal of Neurology, vol. 29, no. 11, Wiley, Aug. 2022, pp. 3389–94. Crossref, https://doi.org/10.1111/ene.15516