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Influenza vaccine typically reduced risk for Guillain-Barré syndrome
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Under normal circumstances, vaccination for influenza appears to decrease an individual’s risk for developing Guillain-Barré syndrome, according to recent findings.
Exceptions include low influenza incidence and/or low vaccine efficacy, researchers said.
“Although [seasonal] influenza vaccination has been shown to reduce influenza-associated illness and death, there is conflicting evidence about whether influenza vaccine may increase the risk of acquiring Guillain-Barré syndrome [GBS],” they wrote in Emerging Infectious Diseases.
Steven Hawken, MSc, of the Institute for Clinical Evaluative Sciences in Toronto, and colleagues created simulation models based on recent peer-reviewed literature to evaluate the risk for GBS in a person who does or does not receive seasonal influenza vaccine.
The researchers established two base-case samples — a woman, aged 45 years; and a man, aged 75 years — to simulate situations of typical patients faced with the choice of influenza vaccination. The simulation showed that the woman had a baseline risk for GBS of 0.97/100,000 person-years (95% CI, 0.62%–1.53%), a 10% chance of influenza onset if unvaccinated, and vaccine effectiveness, if vaccinated, of 61% (95% CI, 30%–52%). The man had a baseline GBS risk of 3.07/100,000 person-years (95% CI, 1.5%–6.27%), a 10% chance of influenza illness without vaccination, and vaccine effectiveness, if vaccinated, of 50% (95% CI, 27%–91%).
The researchers also conducted sensitivity analyses to evaluate the effect of several key covariates on the risk for developing GBS. In the case of the woman, the surplus GBS risk for influenza vaccination vs. no vaccination was –0.36/1 million vaccinations (95% credible interval=−1.22% to 0.28%), indicating a small decrease in absolute risk for GBS. When the man was used as the base-case sample, the excess GBS risk for influenza vaccination vs. no vaccination was −0.42/1 million vaccinations (95% credible interval=–3.68% to 2.44%).
Under normal circumstances — including influenza incidence rates higher than 5% and vaccine effectiveness greater than 60% — vaccination was associated with a decreased risk for GBS.
According to the researchers, even in atypical situations, in which the absolute risk for GBS may be increased by vaccination, the excess risk is small.
“Influenza vaccination is an important population health intervention that reduces morbidity and mortality,” the researchers wrote. “Beyond these benefits, the tendency of influenza vaccination to reduce a person’s overall risk of acquiring GBS under many conditions (although the absolute risk differences are extremely small) should strengthen confidence in the safety of influenza vaccination and allow health professionals to better put the risk of GBS in context when communicating risks and benefits to potential vaccinees.”
Disclosure: The researchers report no relevant financial disclosures.
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