1. Division of Epidemiology and Biostatistics, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa
2. Division of Biostatistics and Bioinformatics, School of Public Health, University of California, San Diego, California, USA
3. Perinatal HIV Research Unit, Faculty of Health Sciences
4. School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg
5. Family Center for Research with Ubuntu, Department of Paediatrics and Child Health, Stellenbosch University, South Africa
6. Department of Medicine, Division of Infectious Diseases, University of California, San Diego, California, USA
7. Desmond Tutu HIV Centre, University of Cape Town, Cape Town, South Africa.