aMelbourne Sexual Health Centre, Alfred Health

bCentral Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University

cCentre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia

Correspondence to Professor Eric P.F. Chow, PhD, Melbourne Sexual Health Centre, 580 Swanston Street, Carlton, VIC 3053, Australia. Tel: +61 393416233; e-mail: [email protected]