Robert Penfold, PhD, Group Health Research Institute, Seattle, WA, Donna Rusinak, BA, Department of Population Medicine, Harvard Pilgrim Health Care Institute, Boston, MA, Tracy Lieu, MD, MPH, Dept of Population Medicine, Harvard Pilgrim Health Care and Harvard Medical School, Boston, MA, Abigail Shefer, MD, MPH, Centers for Disease Control and Prevention, Mark Messonier, PhD, Immunization Services Division, Centers for Disease Control and Prevention, Atlanta, GA and Grace Lee, MD, MPH, Dept of Population Medicine, Harvard Pilgrim Health Care Institute, Harvard Medical School, Children's Hospital Boston, Boston, MA