1. Vaccine Uptake Group, Murdoch Children’s Research Institute, Melbourne, VIC 3052, Australia
2. Department of Paediatrics, The University of Melbourne, Melbourne, VIC 3052, Australia
3. Melbourne Medical School, The University of Melbourne, Melbourne, CIV 3052, Australia
4. Health Protection, Hunter New England Local Health District, Booth Building, Wallsend Health Services Longworth Avenue, Newcastle, NSW 2287, Australia
5. School of Medicine and Public Health, University of Newcastle, Newcastle, NSW 2308, Australia
6. Department of General Medicine, The Royal Children’s Hospital, Melbourne, VIC 3052, Australia