1. Department of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, USA,
2. Women's Global Health Imperative, RTI International, San Francisco, CA, USA
3. South African Medical Research Council HIV Prevention Research Unit, Durban, South Africa
4. UCSF Collaborative Research Programme, Harare, Zimbabwe
5. Perinatal HIV Research Unit, Johannesburg, South Africa
6. University of California, San Francisco, CA, USA
7. Ibis Reproductive Health, Johannesburg, South Africa
8. Women's Global Health Imperative, RTI International, San Francisco, CA, USA, University of California, San Francisco, CA, USA