Objective: To measure the impact of a population-based tracking system on influenza immunization rates.
Design: Thirteen practices with 45 physicians were randomized to a control and two intervention groups.
Setting: Private practices.
Patients: All patients aged 65 years and over who were seen in participating physicians' practices within the preceding two years.
Intervention: In both intervention groups influenza immunization rates for physicians were recorded weekly as cumulative percentages of their target populations, using a specially prepared poster. In addition, postcard reminders were sent to all the patients in one of the intervention groups.
Measurements and main results: Immunization rates in the two intervention groups were 30% higher than in the control group; the control group immunized 50% (2,405/4,772) of its target population, while the poster and poster/postcard groups immunized 66% (1,420/2,149) and 67% (2,427/3,604), respectively.
Conclusion: A population-based strategy that monitors performance can significantly improve rates of influenza immunization in private practices.