Sample
SECONDARY, INFLUENZA
Estimating the effect on vaccination uptake rates to be achieved by the complex intervention is not trivial. From meta-analyses, it is known that effects of around 5% can be achieved by campaigns or interventions that distribute information in a study group, e.g., in the form of brochures, billboard advertisements, flyers, postcards, newsletters, but also by interpersonal communication between GP and patient as well as community education (seminars at schools, workplace) [Thus, it is assumed in the following that the influenza vaccination uptake rate as primary outcome increases by 3% as a result of the intervention. This 3%-increase should be seen as an initial change. To detect this effect in the secondary data analysis with a power of 90% at a significance level of alpha = 5% (two-sided), 17,508 patients would be needed without considering the cluster effect. Based on available anonymised data from previous studies [