1 Department of Social Medicine, University of Bristol, Bristol, UK.
2 Kirby Institute, University of New South Wales, Sydney, NSW, Australia.
3 Centre de recherche du Centre hospitalier de l'Université de Montréal/University of Montreal Hospital Research Centre, University of Montreal, Montreal, Canada.
4 San Francisco Department of Public Health, Substance Use Research, San Francisco, CA, USA.
5 University of California, San Francisco, CA, USA.
6 Division of HIV/AIDS, University of New South Wales, Sydney, Australia.
7 School of Population and Global Health National Drug and Alcohol Research Centre, University of Melbourne, Melbourne, VIC, Australia.
8 Glasgow Caledonian University, School of Health and Life Sciences, Glasgow, UK.
9 Health Protection Scotland, BBV and STI, Glasgow, UK.
10 National Drug and Alcohol Research Centre, University of New South Wales, Randwick, NSW, Australia.
11 University of California San Diego School of Medicine, Division of Global Public Health, San Diego, CA, USA.
12 The University of New South Wales.
13 School of Social and Community Medicine, Centre for Social Research in Health University of Bristol, Bristol, UK.
14 Health Policy Unit, School of Social and Community Medicine, University of Bristol, Bristol, UK.