1. Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
2. Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
3. Department of Health Behavior, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, USA
4. Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC, USA
5. Department of Family Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA