Objective: The objective of this study is to determine whether vaccination against influenza is associated with a reduced risk of acute kidney injury (AKI) in a nationwide cohort of adults aged ≥65 years. Methods: We investigated a total of 13,270 patients aged ≥65 years who were hospitalized for AKI between 2000 and 2013 from Taiwan's National Health Insurance Research Database. Each AKI case was matched with one control subject according to duration of follow-up, age, sex, monthly income, urbanization level, and baseline comorbidities. Odds ratios (ORs) for AKI associated with exposure to the influenza vaccine in the previous year were calculated in a nested case-control analysis. Results: Influenza vaccination in the previous year was associated with a lower risk of AKI (adjusted OR 0.67, 95% confidence interval [CI] 0.63–0.72). Compared with a reference group of unvaccinated individuals with no influenza infection, vaccination with no influenza infection was associated with a lower risk of AKI (adjusted OR 0.68, 95% CI 0.64–0.73). Lack of vaccination and presence of influenza infection was associated with a higher risk of AKI (adjusted OR 1.78, 95% CI 1.57–2.01), whereas the risk of AKI was insignificant in vaccinated patients who developed influenza (adjusted OR 1.01, 95% CI 0.69–1.18). Conclusions: The risk of AKI was 37% lower among older people who received vaccination against influenza in a real-world setting. Further work is required to clarify causality.
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