1. The Kirby Institute, Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia
2. Central Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, VIC 3800, Australia
3. Melbourne Sexual Health Centre, Alfred Health, Carlton, VIC 3053, Australia
4. Comprehensive AIDS Research Center, School of Medicine, Tsinghua University, Beijing 100084, China
5. Centre for Health Behaviors Research, School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, China
6. School of Public Health, Nantong University, Nantong, Jiangsu 226019, China
7. Department of Sociology, Tsinghua University, Beijing 100084, China
8. China Food and Drug Administration Institute of Executive Development, Beijing 100073, China