Abstract
This is the first and largest population-based cohort study to demonstrate that influenza vaccination reduced all-cause mortality and influenza-related hospitalization in elderly individuals with a disability. Purpose: To estimate the protective effect of influenza vaccination in elderly individuals with a disability by conducting a propensity score-matched (PSM), nationwide, population-based cohort study. Methods: Data from Taiwan’s National Health Insurance Research Database were used in this study. Generalized estimating equations (GEEs) were used to compare outcomes between the vaccinated and unvaccinated cohorts. The GEE logit was used to estimate the relative risks of death and hospitalization after influenza vaccination. Adjusted odds ratios (aORs) were used to estimate relative risk. Results: The matching process yielded a final cohort of 272 896 elderly individuals with a disability (136 448 individuals in each cohort). In multivariate GEE analyses, aOR (vaccinated vs. unvaccinated) and 95% confidence interval (CI) of death were 0.70 (0.68–0.72). The aORs (95% CIs) of hospitalization for influenza and pneumonia, respiratory diseases, respiratory failure, heart disease, hemorrhagic stroke, and ischemic stroke were 0.98 (0.95–1.01), 0.96 (0.94–0.99), 0.85 (0.82–0.89), 0.96 (0.93–0.99), 0.85 (0.75–0.97), and 0.89 (0.84–0.95), respectively. The length of stay and medical expenditure exhibited greater reduction in vaccinated elderly individuals with a severe and very severe disability than in unvaccinated elderly individuals. Conclusions: Influenza vaccination reduced all-cause mortality, influenza-related hospitalization, length of stay, and medical expenditure in elderly individuals with a disability. The decrease in the length of stay and medical expenditure because of influenza vaccination was proportional to the severity of disability.
Highlights
Social Security Administration defines disability as the inability to engage in any substantial, gainful activity because of medically determinable physical or mental impairments, which can be expected to result in death or have lasted or can be expected to last for a continuous period of not less than 12 months [1]
The matching process yielded a final cohort of 272 896 elderly individuals with a disability (136 448 individuals each cohort) eligible for the study; their characteristics are summarized in Supplementary
Our Generalized estimating equations (GEEs) analysis revealed that influenza vaccine administration was a significant factor of all-cause mortality, after controlling for disability severity, disability type, age, sex, premium salary, urbanization level, Charlson comorbidity index (CCI) score, catastrophic illness status, long-term care facility residence, outpatient utilization, hospital admission, and preventive care service utilization
Summary
Social Security Administration defines disability as the inability to engage in any substantial, gainful activity because of medically determinable physical or mental impairments, which can be expected to result in death or have lasted or can be expected to last for a continuous period of not less than 12 months [1]. Strong evidence to prove that elderly individuals with a disability are a susceptible population and have a high risk of influenza is not available; no study has shown the beneficial effects of influenza vaccination in elderly individuals with a disability in terms of survival, influenza-related hospitalization, length of stay (LOS), or medical cost. Annual influenza vaccination is recommended for all individuals aged ≥6 months, when the supply of influenza vaccines is limited, individuals at a high risk of complications, people in households of high-risk individuals, and caregivers of high-risk individuals should be the highest-priority recipients [4,5,6].
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