University of Otago Christchurch - Department of Paediatrics, University of Liverpool - Institute of Infection, Veterinary and Ecological Sciences, University of Oxford - Department of Paediatrics, University of Oxford - Department of Paediatrics, University of Oxford - Department of Paediatrics, Great Ormond Street Hospital for Children NHS Foundation Trust, University of Oxford - Nuffield Department of Primary Care Health Sciences, University of Oxford - Centre for Vaccinology and Tropical Medicine, University of Oxford - Nuffield Department of Primary Care Health Sciences, University of Oxford - Department of Paediatrics, University of London - Institute of Infection and Immunity, Alder Hey Children's NHS Foundation Trust - Department of Neurology, St Mary’s Hospital, University of London - Institute of Infection and Immunity, University of Oxford - Department of Paediatrics, University of Liverpool - Institute of Infection, Veterinary and Ecological Sciences, British Columbia Children's Hospital Research Institute - Vaccine Evaluation Center, University of Oxford - Oxford Vaccine Group, Independent and Independent