1. Department of Paediatric Immunology and Infectious Diseases, Wilhelmina Children’s Hospital/University Medical Centre Utrecht, Utrecht, The Netherlands
2. Spaarne Gasthuis Academy, Hoofddorp and Haarlem, The Netherlands
3. Julius Center for Health Sciences and Primary Care, University Medical Centre Utrecht, Utrecht, The Netherlands
4. Department of Primary Care Health Sciences, University of Oxford, Oxford, United Kingdom
5. Department of Family Medicine and Population Health, Centre for General Practice, University of Antwerp, Antwerp, Belgium
6. Vaccine and Infectious Disease Institute, Laboratory of Medical Microbiology, University of Antwerp, Antwerp, Belgium
7. GlaxoSmithKline Biologicals, Rixensart, Belgium