Sarah W. Ball, ScD, Deborah K. Walker, EdD, Sara M.A. Donahue, DrPH, David Izrael, MS, Abt Associates Inc., Cambridge Massachusetts. Jun Zhang, MD, Gary L. Euler, DrPH, Stacie M. Greby, DVM, Megan C. Lindley, MPH, Samuel B. Graitcer, MD, Carolyn Bridges, MD, Walter W. Williams, MD, James A. Singleton, PhD, Immunization Svcs Div, National Center for Immunization and Respiratory Diseases; Taranisia F. MacCannell, PhD, Div of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, CDC. Corresponding contributors: Gary Euler, geuler@cdc.gov, 404-639-8742; Jun Zhang, jzhang5@cdc.gov, 404-718-4867.