1 Oxford Uehiro Centre for Practical Ethics, University of Oxford, Oxford, United Kingdom.
2 Oxford Uehiro Centre for Practical Ethics, University of Oxford, Oxford, United Kingdom; Murdoch Children's Research Institute, Melbourne, Victoria, Australia.
3 Department of General Medicine, The Royal Children's Hospital and Vaccine Uptake Group Murdoch Children's Research Institute, Melbourne, Victoria, Australia; Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia.