1. Communicable Diseases, Health Protection Branch, Public Health Division, Department of Health, Victoria, Melbourne, Australia
2. National Centre for Epidemiology and Population Health, Australian National University, Canberra, Australia
3. WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
4. School of Population and Global Health, University of Melbourne, Melbourne, Australia
5. Department of Immunology and Microbiology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
6. Department of Infectious Diseases, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia