1. HIV and STI Department, Centre for Infectious Disease Surveillance and Control, Public Health England, Colindale, London, United Kingdom
2. Virus Reference Department, Microbiology Services Colindale, London, United Kingdom
3. MRC Biostatistics Unit, Institute of Public Health, Cambridge, United Kingdom
4. Department of Infectious Disease Epidemiology, Imperial College London, United Kingdom
5. MRC Clinical Trials Unit, London, United Kingdom