1 Marshfield Clinic Research Institute, Marshfield, Wisconsin.
2 Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia; Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia; Cancer Prevention and Control Program, Winship Cancer Institute, Atlanta, Georgia; Emory Vaccine Center, Emory University, Atlanta, Georgia.