Association between Stroke Risk and Influenza Vaccination in Patients with Gout: A Nationwide Population-Based Study

The risk of stroke in patients with gout is high. The effect of vaccines in lowering the stroke risk in patients with gout remains unclear. We retrospectively analyzed 23,949 patients with gout (age >= 55 years) from the National Health Insurance Research Database over a 12-year period. The patients were divided into vaccinated (n = 11,649) and unvaccinated groups (n = 12,300). Overall, the vaccinated group had significantly lower risks of all stroke, hemorrhagic stroke, and ischemic stroke than the unvaccinated group (adjusted hazard ratio [aHR], 0.59 and 95% confidence interval [CI], 0.55-0.63; aHR, 0.60 and 95% CI, 0.49-0.73; and aHR, 0.60 and 95% CI, 0.55-0.65, respectively). The association appeared to be dose-dependent for both hemorrhagic and ischemic stroke (hemorrhagic stroke: aHR, 0.81 and 95% CI, 0.61-1.08; aHR, 0.80 and 95% CI, 0.62-1.02; and aHR, 0.37 and 95% CI, 0.28-0.48; ischemic stroke: aHR, 0.83 and 95% CI, 0.74-0.94; aHR, 0.73 and 95% CI, 0.65-0.81; and aHR, 0.42 and 95% CI, 0.38-0.47 for patients vaccinated 1, 2 or 3, and >= 4 times, respectively, during the follow-up period). Patients with a history of atrial fibrillation did not have a lower risk of hemorrhagic stroke even after receiving four vaccinations (aHR, 0.59; 95% CI, 0.25-1.38). Influenza vaccination was associated with a lower risk of all stroke in people with gout, and the association appeared to be dose-dependent.