The impact of influenza vaccination on hospitalizations and mortality among frail older people.

OBJECTIVES The objective of this study was to evaluate the benefits of influenza vaccination against hospitalization and mortality on frail elderly people. DESIGN The design was a population-based retrospective cohort study. SETTING Taiwan's National Health Insurance claims data. PARTICIPANTS Participants were 5063 frail seniors, followed up for four years. MEASUREMENTS Measurements included age, gender, socioeconomic status, living areas, use of annual health examinations, comorbid conditions, use of influenza vaccine, frailty as defined by the Adjusted Clinical Group, hospitalization, and mortality in the observation period. The efficacy was presented as comparing ever versus never vaccinated people during the entire study period without regard to seasons. RESULTS Compared with those without influenza vaccination, vaccinated elderly individuals were younger, more likely to be men, have higher socioeconomic status, live in rural areas, have a higher rate of receiving a health examination, and have similar medical conditions. In the Cox proportional hazards analysis, influenza vaccination reduced by 7% the risk of hospitalization (95% confidence interval [CI] 0.86-0.99) and by 44% the risk of mortality (95% CI 0.51-0.62). CONCLUSION Influenza vaccination was effective against hospitalization and mortality among the frail elderly. These results uphold the current universal influenza vaccination policy, and encourage policymakers to adopt strategies to improve vaccination use.