1 Department of Paediatrics, Wilhelmina Children's Hospital, University Medical Centre Utrecht, Utrecht, Netherlands.
2 Department of Pediatrics, Paris 7 University, Paris, France.
3 Department of Pediatrics, University of Lübeck, Lübeck, Germany.
4 Department of Medicine and Surgery, Pediatric Clinic, Pietro Barilla Children's Hospital, University of Parma, Parma, Italy.
5 Deparment of Vaccinology, Ministry of Health, Madrid, Spain.
6 Department of Biomedical Science, Research Center in Health Administration, University of Milan, Milan, Italy.
7 European Foundation for the Care of Newborn Infants (EFCNI), Munich, Germany.
8 Department of Pediatrics and Child Health, Nihon University School of Medicine, Tokyo, Japan.
9 Department of Respiratory Medicine, Beijing Children's Hospital, Capital Medical University, Beijing, China.
10 Department of Pediatrics, School of Medicine, University of Thessaly, Larissa, Greece.
11 Faculty of Medicine, Institute for Life Sciences, University of Southampton, Southampton, United Kingdom.
12 National Institute for Health Research (NIHR) Southampton Clinical Research Facility, NIHR Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
13 Pediatric and Infectious Diseases Unit, Bambino Gesù Children Hospital, Rome, Italy.