1. Paediatric Immunology and Infectious Diseases, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, The Netherlands
2. Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, USA
3. Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
4. Spaarne Gasthuis Academie, Spaarne Gasthuis, Hoofddorp, The Netherlands