1. Department of Behavioral and Social Sciences, Brown University School of Public Health, Providence, Rhode Island, USA.
2. Perinatal HIV Research Unit, University of the Witwatersrand, Johannesburg, South Africa.
3. Office of AIDS and TB, UnSouth African Medical Research Council, Cape Town, South Africa.
4. Centre of Excellence in Epidemiological Modelling and Analysis, Stellenbosch University, Stellenbosch, South Africa.
5. Biostatistics Unit, UnSouth African Medical Research Council, Cape Town, South Africa.
6. Division of Epidemiology and Biostatistics, Department of Global Health, Stellenbosch University, Cape Town, South Africa.
7. Health Systems Research Unit, UnSouth African Medical Research Council, Cape Town, South Africa.