1. Pompeu Fabra University, Barcelona, Spain
2. Centre for Epidemiological Studies on Sexually Transmitted Infections and HIV/AIDS of Catalonia (CEEISCAT), Catalan Institute of Oncology (ICO), Public Health Agency of Catalonia (ASPCAT), Barcelona, Spain
3. Centros de Investigación Biomédica en Red Epidemiología y Salud Pública (CIBERESP), Spain
4. Department of Paediatrics, Obstetrics, Gynaecology and Public Health of the Autonomous University of Barcelona, Bellaterra, Barcelona, Spain
5. Sexually Transmitted Infections Unit, Drassanes Primary Health Centre, Catalan Institute of Health, Barcelona, Spain
6. Epidemiological Surveillance Unit, Lleida, Spain
7. Care Programme for sexual and reproductive health, Badalona Care Services, Barcelona, Spain
8. Care programme for sexual and reproductive health, Catalan Institute of Health, Barcelona, Spain
9. Care programme for sexual and reproductive health, Catalan Institute of Health, Sabadell, Spain
10. Salt Primary Health Centre, Catalan Institute of Health, Girona, Spain
11. Department of Andrology, Puigvert Foundation, Barcelona, Spain
12. Sexually Transmitted Infections Unit, Cerdanyola Primary Health Centre, Catalan Institute of Health, Barcelona, Spain
13. Care programme for sexual and reproductive health, Catalan Institute of Health, Esquerra de l’Eixample, Barcelona, Spain
14. Care programme for sexual and reproductive health, Catalan Institute of Health, Manresa, Barcelona, Spain
15. The members of the group are listed at the end of the article