1. The Northern Contraception, Sexual Health and HIV Service, Manchester Royal Infirmary, Manchester, UK
2. Chelsea and Westminster Hospital, London, UK
3. Imperial College London, London, UK
4. South Tees Hospitals NHS Foundation Trust, Middlesbrough, UK
5. North Middlesex University Hospital, London, UK
6. Gilead Sciences Ltd, London, UK
7. Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK