1. Department of Paediatrics and Adolescent Medicine, Aarhus University Hospital, Aarhus, Denmark
2. Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
3. Department of Paediatrics and Adolescent Medicine, Nordsjaellands Hospital, Hillerod, Denmark
4. Department of Paediatrics and Adolescent Medicine, Herlev Hospital, Herlev, Denmark
5. Department of Paediatrics and Adolescent Medicine, Hvidovre University Hospital, Copenhagen, Denmark
6. Department of Paediatrics and Adolescent Medicine, Odense University Hospital, Odense, Denmark
7. Department of Paediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark