1. Health Systems Research Unit, South African Medical Research Council, Cape Town 7501, South Africa
2. Department of Psychology, University of Cape Town, Cape Town 7700, South Africa
3. Division of Social and Behavioural Sciences, School of Public Health and Family Medicine, University of Cape Town, Cape Town 7925, South Africa
4. School of Public Health and Family Medicine, University of Cape Town, Cape Town 7925, South Africa
5. Biostatistics Research Unit, South African Medical Research Council, Durban 4091, South Africa
6. Office of AIDS and TB Research, South African Medical Research Council, Pretoria 0001, South Africa
7. Department of Basic Education, Government of South Africa, Pretoria 0001, South Africa
8. Division of Infectious Diseases, Department of Internal Medicine, Steve Biko Academic Hospital and University of Pretoria, Pretoria 0002, South Africa