Effectiveness of an influenza vaccine programme for care home staff to prevent death, morbidity, and health service use among residents: Cluster randomised controlled trial

Objective: To determine whether vaccination of care home staff against influenza indirectly protects residents. Design: Pair matched cluster randomised controlled trial. Setting: Large private chain of UK care homes during the winters of 2003-4 and 2004-5. Participants: Nursing home staff (n = 1703) and residents (n = 2604) in 44 care homes (22 intervention homes and 22 matched control homes). Interventions: Vaccination offered to staff in intervention homes but not in control homes. Main outcome measures: The primary outcome was all cause mortality of residents. Secondary outcomes were influenza-like illness and health service use in residents. Results: In 2003-4 vaccine coverage in full time staff was 48.2% (407/884) in intervention homes and 5.9% (51/859) in control homes. In 2004-5 uptake rates were 43.2% (365/844) and 3.5% (28/800). National influenza rates were substantially below average in 2004-5. In the 2003-4 period of influenza activity significant decreases were found in mortality of residents in intervention homes compared with control homes (rate difference - 5.0 per 100 residents, 95% confidence interval - 7.0 to - 2.0) and in influenza-like illness (P = 0.004), consultations with general practitioners for influenza-like illness (P = 0.008), and admissions to hospital with influenza-like illness (P = 0.009). No significant differences were found in 2004-5 or during periods of no influenza activity in 2003-4. Conclusions: Vaccinating care home staff against influenza can prevent deaths, health service use, and influenza-like illness in residents during periods of moderate influenza activity.