1. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA
2. Institute of Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA
3. Department of Epidemiology and Biostatistics, University of California , San Francisco, California, USA
4. Gilead Sciences , Foster City, California , USA
5. Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA
6. Division of Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA