1. Department of Family Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
2. Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
3. Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
4. Division of Public Health, Immunization Branch, North Carolina Department of Health and Human Services, Raleigh, North Carolina, USA
5. Department of Health Behavior, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
6. Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA