1. Vanderbilt Institute for Global Health, Vanderbilt University Medical Center, Nashville, TN, USA
2. Department of Health Policy, Vanderbilt University Medical Center, Nashville, TN, USA
3. MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt) School of Public Health, Faculty of Health Sciences, Johannesburg, South Africa
4. Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN, USA
5. School of Nursing and Public Health, College of Health Sciences, University of KwaZulu Natal, Durban, South Africa