1. Kenyatta National Hospital, Research and Programs, P.O. Box 20723-00202, Nairobi, Kenya.
2. Department of Global Health, University of Washington, Seattle, United States of America (USA).
3. Department of Pediatrics and Child Health, University of Nairobi, Nairobi, Kenya.
4. Department of Epidemiology, University of Washington, Seattle, USA.
5. Kenya Medical Research Institute, Kisumu, Kenya.
6. National AIDS and STI Control Program, Ministry of Health, Nairobi, Kenya.