Statewide immunization information systems (IISs) now exist in all states to track vaccinations. They have not yet been used for influenza vaccine R/R because of lack of evidence for their effectiveness and a lack of a template for IIS-based reminder/recall. The investigators have united two leading immunization research groups (Denver, CO and Rochester, NY) to assess the impact of centralized IIS-based influenza vaccine reminder/recall, and to evaluate the effect of intensity of recall (1 v. 2. v. 3 reminders) over usual care. The investigators will also develop tools to aid other states in creating efficient IIS reminder/recall systems. The investigators will also develop tools to aid other states in creating efficient IIS reminder/recall systems for seasonal and possible pandemic influenza outbreaks.