1. Imperial College, London, London W2 1PG, UK.
2. EUROPRISE Network of Excellence on Microbicides and Vaccines ().
3. AVAC: Global Advocacy for HIV Prevention, New York, NY 10027, USA.
4. Medical Research Council Clinical Trials Unit, London NW1 2DA, UK.
5. Office of the Deputy Executive Director, Programme Branch, Joint United Nations Programme on HIV/AIDS, CH-1211 Geneva, Switzerland.