* Abbreviations: ACIP — : Advisory Committee on Immunization Practices CDC — : Centers for Disease Control and Prevention SLV — : school-located mass vaccination TIV — : trivalent influenza vaccine For many years, the Advisory Committee on Immunization Practices (ACIP) for the Centers for Disease Control and Prevention (CDC) focused its vaccination policy on persons at higher risk for influenza complications (eg, older adults, children and adults with certain high-risk conditions, pregnant women) and their contacts (eg, household contacts, health care personnel). Unfortunately, although vaccination coverage rates varied, they remained low for most adult and pediatric high-risk groups, other than persons aged ≥65 years.1 In conjunction with the recognition that influenza vaccination recommendations for high-risk target populations were not being optimally implemented, the adverse effects of influenza illness on all children was increasingly recognized. This led to the expansion of vaccination recommendations for children, beginning in 2002, when influenza vaccination was “encouraged” for children aged 6 through 23 months, and in 2004, when a full recommendation was issued for this age group.2,3 That recommendation was based largely on studies documenting that these young children had influenza-related hospitalization rates that were comparable to hospitalization rates in older persons with underlying risk conditions who were targeted to receive influenza vaccine.4–6 Full recommendation was added for other groups who are at risk, such as adults and children with neuromuscular and other conditions that can compromise respiratory function or the handling of respiratory secretions, as data became available.7 The gradual, incremental, group-by-group expansion of influenza recommendations to additional age and risk groups was challenging for providers and the public. In the ensuing years, immunization experts, professional organizations, and other stakeholders debated the advantages and challenges of expanding routine influenza vaccination to all persons in the United States.8–10 At a meeting of immunization and … Address correspondence to Richard Schieber, MD, MPH, Epidemiology and Analysis Program Office, Office of Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS E33, Atlanta, GA 30333. E-mail: rschieber{at}cdc.gov