Protective effect of influenza vaccination on outcomes in geriatric stroke patients: A nationwide matched cohort study

Background and aims: The effects of influenza vaccination (IV) on stroke outcomes are unclear. The purpose of this study is to evaluate the outcomes after stroke in elderly individuals who have received an IV. Methods: We used Taiwan's National Health Insurance Research Database 2000–2009 claims data to conduct a nested stroke cohort study including 148,909 hospitalized stroke patients aged 66 years and older. Using a matching procedure by propensity score, we selected 25,248 stroke patients with IV and 25,248 stroke patients without IV for comparison. Logistic regression was used to calculate the odds ratios (ORs) and 95% CIs of post-stroke complications and in-hospital mortality associated with IV. Results: Stroke patients with IV had significantly lower risks of post-stroke pneumonia (OR = 0.79; 95% CI, 0.74–0.83), septicemia (OR = 0.78; 95% CI, 0.70–0.86), urinary tract infection (OR = 0.87; 95% CI, 0.83–0.92), and 30-day in-hospital mortality (OR = 0.60; 95% CI, 0.54–0.67) compared with non-IV stroke patients. Vaccinated stroke patients also had shorter hospital stays (p < 0.0001) and less medical expenditures (p < 0.0001) during stroke admission than the control group. Lower rates of post-stroke adverse events in patients with IV were noted in both sexes of all age groups with various types of stroke. Conclusions: Stroke patients with IV showed fewer complications and lower mortality compared with non-IV patients. These findings suggest the urgent need to promote IV for this susceptible population of stroke patients.