1. Kirby Institute, Level 6, Wallace Wurth Building, UNSW Sydney, Kensington, Sydney, 2052Australia.
2. School of Public Health and Community Medicine, UNSW Sydney, Sydney, Australia.
3. Sydney School of Public Health, The University of Sydney, Sydney, Australia.
4. National Centre for Immunisation, Research and Surveillance, Sydney, Australia.
5. Centre for the Evaluation of Vaccination, University of Antwerp, Antwerp, Belgium.