Effectiveness of a theory-informed intervention to increase care home staff influenza vaccination rates: a cluster randomised controlled trial

Background: Care home staff's (CHS's) influenza vaccination rate in England is 30%-40%, below the 75% WHO recommendation. We describe the effectiveness of a theory-informed and feasibility-tested intervention (in-home clinics; posters/videos to address vaccination hesitancy and care home financial incentives for uptake) to improve CHS vaccination rates. Method: Recruited care homes in England with CHS vaccination rates <40% were randomised at the home level for intervention or control. Assuming a change in CHS vaccinated from 55% to 75%, 20% attrition, and 90% power, we required 39 homes per arm. Monthly data were collected throughout flu season. The difference in vaccination rates between the arms was compared using the intention-to-treat principle and a random effect logistic regression model. Findings: The mean % vaccination rate was 28.6% in control (n = 35) and 32.7% in intervention (n = 35) [odds ratio (OR) = 1.29, 95% confidence interval (CI): 0.68-0.4, P = .435]. In a sub-analysis, including only homes receiving at least one clinic, control was 28.6% (n = 35) and intervention was 41.7% (n = 23) (OR = 2.08, 95% CI: 0.67-2.70, P = .045). Interpretation: No effect on vaccination status was demonstrated. Within homes receiving clinics, a significant increase was observed. Process evaluation evidence suggests that starting 3 months into the influenza season partially explains this. Further evaluation initiating FluCare earlier is warranted.