Effectiveness of High-Dose Influenza Vaccination on Hospitalizations of Older Adults in US Nursing Homes: Results. from a Cluster-Randomized Controlled Trial

Abstract

Background. Response to influenza (flu) vaccine declines with age, reducing clinical effectiveness. Our primary objective was to determine whether a more immunogenic Fluzone high-dose vaccine (HD), compared with a Fluzone standard-dose vaccine (SD) could reduce hospitalizations among nursing home (NH) residents. Methods. In this pragmatic, comparative effectiveness, cluster-randomized trial, enrolled NHs were randomized to administer either HD or SD vaccine to long-stay residents for the 2013-2014 season. Facilities were also allocated to free vaccine for staff or usual procedure in a 2 x 2 factorial design. Data were collected from CMS under data-use agreements and from enrolled facilities. All analyses were by Intent- To-Treat.We analyzed hospitalization incidence using marginal Poisson regression accounting for clustering of residents within facilities, and adjusting for a priori facility and resident covariates.We analyzed secondary outcomes (mortality, activities of daily living) using Cox proportional hazards and logistic regression. Results. We randomized 823 facilities with 53,008 long-stay residents; facility and resident characteristics were similar between arms. Flu A/H1N1 was the dominant flu strain during the study period. Incidence of hospitalization was significantly lower in HD than SD facilities for all-causes (adjusted RR = 0.951, 95% CI 0.907-.996, P = 0.0347) and respiratory conditions (ARR = 0.883, CI 0.787-0.989, P = 0.032) and lower but NS so for pneumonia and influenza. Conclusion. High-dose flu vaccine reduces risk of all-cause hospitalization and hospitalization for respiratory conditions in long-term care residents in an A/H1N1 dominant season. Registration. NCT01815268 Funding. Sanofi Pasteur.