1. E-Health unit, Research Department of Primary Care and Population Health, University College London, London, UK
2. PRIMENT Clinical Trials Unit, Research Department of Primary Care and Population Health, University College London, London, UK
3. Barts and The London School of Medicine and Dentistry, Barts Sexual Health Centre, Queen Mary University of London, St Bartholomew’s Hospital, London, UK
4. Research Department of Clinical, Educational and Health Psychology, University College London, London, UK
5. Homerton Sexual Health Services, Homerton Teaching Hospitals, London, UK
6. Department of Reproductive Health, Institute for Women’s Health, University College London, London, UK
7. Department of Infection and Population Health, University College London, London, UK
8. Engineering and Digital Arts, University of Kent, Kent, UK