OBJECTIVE: To improve influenza vaccination rates for high-risk children and adolescents. METHODS: During the 2004-5 influenza season, 5 regional cystic fibrosis (CF) centres, 6 hospital clinics that participated in a similar initiative the previous year, 4 new hospital clinics, and 39 community-based paediatric practices implemented a multicomponent change package consisting of nine improvement strategies designed to increase immunisation of high-risk patients. Each site was encouraged to adopt and customize the improvement strategies to meet their specific culture and needs. The main outcome measure was the proportion of the target population immunised. Surveys sent to the community practices were summarised. RESULTS: The intervention targeted a total of 18 866 high-risk children and 9374 (49.7%) received the influenza vaccination. Community-based practices that actively participated in the collaborative reported using significantly more intervention strategies (mean (SD) 7.4 (2.3) vs 4.6 (1.5), respectively, p = 0.001) and achieved higher immunisation rates (59.3% (13.6%) vs 43.7% (20.5%), respectively, p = 0.01) than non-participating practices. The most frequently implemented change concepts were posters in the office, walk-in clinics or same-day appointments and reminder phone calls. The interventions deemed most helpful were weekend or evening "flu shot only" sessions, walk-in or same-day appointments, reminder calls and special mailings to families. CONCLUSIONS: Implementation of the change package, based on evidence and diffusion of innovation theory, resulted in higher immunisation rates than typically reported in the medical literature, especially for the community-based primary care practices.