1. Institute for Global Health, University College London, London, UK
2. Department of Primary Care and Public Health, Brighton and Sussex Medical School, Brighton, UK
3. Medical School, University of Exeter, Exeter, UK
4. Research Department of Primary Care and Population Health, University College London, London, UK
5. Brighton and Sussex University Hospitals NHS Trust, Brighton, UK
6. London Hub for Trials Methodology Research, Medical Research Council Clinical Trials Unit, London, UK
7. Sexually Transmitted Infection Surveillance, Public Health England, London, UK
8. Department of Health Services Research and Policy, London School of Hygiene & Tropical Medicine, London, UK