The purpose of this document is to describe planning scenarios for state and local governments to target high-priority populations for vaccination in order to reduce the health and societal impact of the novel H1N1 influenza virus. Background Data from U.S. and international sources suggests that it is appropriate to plan for a vaccination program to reduce the health and societal impacts of the novel H1N1 influenza virus. In order to increase the probability of success of such a program, planning scenarios should be provided to state and local health authorities promptly. Planning scenarios can facilitate readiness to implement specific plans...