1. Department of Sociology, Universidad Pública de Navarra , Av. Cataluña s/n, 31006 Pamplona , Spain
2. I-COMMUNITAS—Institute for Advanced Social Research, Universidad Pública de Navarra , Av. Cataluña s/n, 31006 Pamplona , Spain
3. Department of Public Health and Maternal & Child Health, Faculty of Medicine, Universidad Complutense de Madrid , Madrid , Spain
4. CIBER Epidemiología y Salud Pública (CIBERESP) , Instituto de Salud Carlos III, Madrid , Spain
5. Infectious Diseases Department, Istituto Superiore di Sanità , Rome , Italy