Current influenza vaccination recommendations focus on immunizing high-risk people; however, influenza mortality and morbidity remain elevated. U.S. policymakers are considering expansion of flu vaccination recommendations to include school-age children (ages 5-18). Children are at risk for flu and propagate epidemic spread. Immunizing children at school offers an efficient approach to covering this population. This study examines the cost consequences of a large multistate, school-based influenza immunization program. The results show that immunization reduces disease among children and adults and is cost-saving to society. An epidemiologically based influenza immunization policy might be an important supplement to the existing risk-based policy.