1. Department of Health Services Research and Policy; London School of Hygiene and Tropical Medicine; 15-17 Tavistock Place London WC1H 9SH U.K.
2. Imperial Clinical Trials Unit; Imperial College London; 68 Wood Lane London W12 7RH U.K.
3. Section of Infectious Diseases, Department of Medicine; Imperial College London; London W2 1PG U.K.
4. HIV i-Base