Efficacy of influenza vaccine among elderly patients by physical activity status

Objective: Although many studies have shown the usefulness of influenza vaccine in elderly in-patients, the efficacy of vaccination with regard to the daily physical activities of patients has not been fully evaluated. To address this issue, we correlated the use of medical resources with vaccination status in patients categorized according to their daily activity levels. Methods: The subjects comprised 237 in-patients at or above 51 years of age, who were hospitalized in the long-term care unit of a Japanese hospital between January and March, 1999. The vaccination status and medical resources use (i.e., oral antibiotics, injected antibiotics, blood cell count, chest X-ray) of each patient were recorded, and the patients were assigned to three subgroups, based on daily life activity scores. Results: Vaccinated in-patients in the 'bed-bound' category required fewer medical resources, i.e., oral antibiotics (-2.29 days, P<0.05), injected antibiotics (-5.02 days, P<0.001), blood cell counts (-4.66 times, P<0.001), and chest X-rays (-4.31 times, P<0.001), compared with unvaccinated in-patients. There were no significant differences in treatment parameters between vaccinated and unvaccinated patients in the 'partly limited' or 'no limitation' categories. Conclusions: It is suggested that influenza vaccination significantly reduces the need for medical treatment only among those in-patients who are the least physically active. Further studies are required to replicate these findings, and to elucidate the underlying reasons for this reduction.