1. Division of Epidemiology and Biostatistics
2. Centre for Infectious Disease Epidemiology and Research, School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa
3. ICAP, Columbia University, Mailman School of Public Health, New York, NY, USA
4. Department of Obstetrics and Gynaecology, New Somerset Hospital, University of Cape Town, Cape Town, South Africa
5. ANOVA Health Institute, Johannesburg, South Africa
6. College of Physicians and Surgeons, Columbia University, New York, NY, USA