Abstract
Background. Influenza (FLU) produces a substantial health and cost burden for the elderly. FLU vaccine effectiveness decreases with age. High-dose (HD) vaccine has quadruple the antigen of standard-dose (SD) vaccine and is more immunogenic and effective in ambulatory persons ≥65 years old. We conducted a large pragmatic 2 × 2 factorial-cluster RCT to evaluate the clinical effectiveness of HD relative to SD FLU vaccine and of access to free SD vaccine for staff in a long-term care setting. Method. Medicare certified nursing homes (NHs) within 50 miles of a CDC FLU reporting city were eligible to participate. NH's leadership agreed to random assignment to either HD (Fluzone High Dose vaccine) or SD (Fluzone vaccine) as the standard of care for their NH residents. Half of the NHs were randomly allocated to free SD vaccine for staff. Only residents ≥65 years of age living in study NHs for >90 days were analyzed. We used Vital Status and Minimum Data Set 3.0 records to determine pre-specified outcomes: (1) all-cause hospitalization (primary), (2) mortality, and (3) functional decline. We performed intent-to-treat analysis at the resident level using multivariable logistic and Cox proportional hazards regression models (SAS 9.4), accounting for clustering by facility and adjusting for a priori baseline covariates (age, functional status, cognitive function, chronic heart failure). Result. We randomized 823 NHs into four arms (193 Resident HD/Staff Free, 216 HD/Usual Care, 226 SD/Free, 188 SD/Usual Care) in 38 states during November 2013–March 2014 in a mostly A(H1N1) FLU season. NHs housed 53,035 eligible residents (72% female, 76% white), and similar group characteristics. There were no significant interactions between the two interventions. Hospitalization was significantly reduced among HD versus SD group residents (19.7% versus 20.9%, adjusted odds ratio 0.930; 95% CI: 0.875–0.988; p = 0.020). To prevent a resident from being hospitalized, 81 (CI: 53–182) residents needed to receive HD rather than SD vaccine. We observed no significant differences in mortality or functional decline rates. Conclusion. HD FLU vaccination appears to reduce all-cause hospitalization from a NH during a predominantly A(H1N1) season. (Clinicaltrials.gov: NCT01815268.) Disclosures. S. Gravenstein, Sanofi Pasteur: Consultant, Grant Investigator, Scientific Advisor and Speaker's Bureau, Consulting fee, Grant recipient, Research support and Speaker honorarium. Merck: Scientific Advisor, Consulting fee; H. E. Davidson, Sanofi Pasteur: Research Contractor, Research support; L. Han, Sanofi Pasteur: Research Contractor, Research grant
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