1. Grup de Recerca Infermera en Vulnerabilitat i Salut (GRIVIS). Nursing Department. Faculty of Medicine. Autonomous University of Barcelona, Spain
2. Centre for Epidemiological Studies of HIV/SIDA and STI of Catalonia (CEEISCAT), Health Department, Generalitat de Catalunya, Badalona, Catalunya, Spain
3. Institute for Health Science Research Germans Trias i Pujol (IGTP), Badalona, Spain
4. Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Instituto de Salud Carlos III, Madrid, Comunidad de Madrid, Spain