1. Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
2. Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
3. Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
4. Gilead Sciences, Foster City, California, USA