Effect of Influenza Vaccination of Nursing Home Staff on Mortality of Residents: A Cluster‐Randomized Trial

Abstract

OBJECTIVES: To evaluate the effect of staff influenza vaccination on all‐cause mortality in nursing home residents. DESIGN: Pair‐matched cluster‐randomized trial. SETTING: Forty nursing homes matched for size, staff vaccination coverage during the previous season, and resident disability index. PARTICIPANTS: All persons aged 60 and older residing in the nursing homes. INTERVENTION: Influenza vaccine was administered to volunteer staff after a face‐to‐face interview. No intervention took place in control nursing homes. MEASUREMENTS: The primary endpoint was total mortality rate in residents from 2 weeks before to 2 weeks after the influenza epidemic in the community. Secondary endpoints were rates of hospitalization and influenza‐like illness (ILI) in residents and sick leave from work in staff. RESULTS: Staff influenza vaccination rates were 69.9% in the vaccination arm versus 31.8% in the control arm. Primary unadjusted analysis did not show significantly lower mortality in residents in the vaccination arm (odds ratio=0.86, P=.08), although multivariate‐adjusted analysis showed 20% lower mortality (P=.02), and a strong correlation was observed between staff vaccination coverage and all‐cause mortality in residents (correlation coefficient=−0.42, P=.007). In the vaccination arm, significantly lower resident hospitalization rates were not observed, but ILI in residents was 31% lower (P=.007), and sick leave from work in staff was 42% lower (P=.03). CONCLUSION: These results support influenza vaccination of staff caring for institutionalized elderly people.