1. Julius Center for Health Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
2. Vaccine Research Centre, University of Tampere Medical School, Tampere, Finland
3. Department of Women and Child Health, University of Padua, Padua, Italy
4. Department of Paediatrics, Prof.-Hess-Kinderklinik and Research Laboratory, Bremen, Germany
5. Department of Paediatrics and Healthcare Research Institute of Santiago, University of Santiago de Compostela, Santiago de Compostela, Spain