Effects of influenza vaccination on mortality among frail, community-living elderly patients: An observational study

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Abstract
Background and aims: The annual winter outbreak of influenza is one of the major causes of morbidity and mortality among frail elderly people. The aims of the present study were to describe the prevalence of vaccination against influenza in a population of older people living in the community, and to examine the relationship between influenza vaccination and mortality. Methods: This was an observational cohort study. We analyzed data from the Italian Silver Network Home Care project, which collected data on patients admitted to home care programs. A total of twelve Home Health Agencies participated in this project, evaluating the implementation of the Minimum Data Set for Home Care (MDS-HC) instrument. A total of 2082 patients were enrolled in the present study. The main outcome measures were prevalence of vaccination against influenza and 1-year survival according to vaccination status. Results: Nearly half the subjects in our Italian sample did not receive influenza vaccination. During a mean follow-up period of 10 months from initial MDS-HC assessment, 167 vaccinated subjects (15%) died compared with 192 non-vaccinated subjects (19%) (p=0.01). After adjusting for age, gender, and all variables significantly different between vaccinated and non-vaccinated subjects at baseline (functional and cognitive impairment, number of diseases, number of medications, depression, pressure ulcers), vaccinated subjects were less likely to die than non-vaccinated ones (RR 0.73; 95% CI 0.56–0.94). Conclusions: Vaccination against influenza has important prognostic implications for frail geriatric patients living in the community, independent of age, gender, and other clinical and functional variables. Despite extensive scientific evidence, recommendations for annual vaccination against influenza among subjects at higher risk have never been adequately implemented.