1. Centre for Trials Research, Cardiff University, Cardiff, UK
2. The Welsh Centre for Primary and Emergency Care Research (PRIME), Division of Population Medicine, Cardiff University, Cardiff, UK
3. School of Healthcare Sciences, College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
4. Cardiff and Vale University Health Board, Department of Sexual Health, Cardiff Royal Infirmary, Cardiff, UK
5. Public Health Wales NHS Trust, Public Health Wales, Cardiff, UK
6. 1Centre for Trials Research, Cardiff University, Cardiff, UK
7. 2The Welsh Centre for Primary and Emergency Care Research (PRIME), Division of Population Medicine, Cardiff University, Cardiff, UK
8. 3School of Healthcare Sciences, College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
9. 4Cardiff and Vale University Health Board, Department of Sexual Health, Cardiff Royal Infirmary, Cardiff, UK
10. 5Public Health Wales NHS Trust, Public Health Wales, Cardiff, UK