1. Department of Pediatric Infectious Diseases and Immunology, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, the Netherlands
2. Vaccine and Infectious Disease Institute, Laboratory of Medical Microbiology, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium
3. Department of Primary and Interdisciplinary Care-Centre for General Practice, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium
4. Department of Epidemiology and Social Medicine, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium
5. Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, United Kingdom
6. GlaxoSmithKline Vaccines, Wavre, Belgium
7. Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands