Victorian Cytology Service, PO Box 310, East Melbourne, Vic. 8002, Australia. National Centre for Immunisation Research and Surveillance, The Children’s Hospital at Westmead, Discipline of Paediatrics and Child Health, School of Public Health, University of Sydney, Sydney, NSW 2006, Australia. Melbourne Sexual Health Centre, 580 Swanston Street, Carlton, Vic. 3053, Australia. School of Population Health, University of Melbourne, Carlton, Vic. 3053, Australia. Clinical Microbiology and Infectious Diseases, Royal Women’s Hospital, Melbourne, Vic. 3052, Australia. Department of Clinical Microbiology, Royal Children’s Hospital, Melbourne, Vic. 3052, Australia. Faculty of Medicine, Dentistry and Health, Department of Obstetrics and Gynaecology, University of Melbourne, Melbourne, Vic. 3053, Australia. Murdoch Children’s Research Institute, University of Melbourne, Melbourne, Vic. 3052, Australia. Corresponding author. Email: jbrother@vcs.org.au