1. Health Economics and Epidemiology Research Office, Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
2. HIV Prevention Research Unit, South African Medical Research Council, Cape Town, South Africa
3. CAPRISA-MRC HIV-TB Pathogenesis and Treatment Research Unit, University of KwaZulu-Natal, Durban, South Africa
4. Department of Global Health, Boston University School of Public Health, Boston, MA, United States of America