1. Department of Epidemiology Research, Statens Serum Institut , Copenhagen, Denmark
2. Haematology, Danish Cancer Society Research Centre, Danish Cancer Society , Copenhagen, Denmark
3. Section of Epidemiology, Department of Public Health, University of Copenhagen , Copenhagen, Denmark
4. Department of Paediatrics and Adolescent Medicine, University Hospital Rigshospitalet , Copenhagen, Denmark
5. Department of Clinical Medicine, University of Copenhagen , Copenhagen, Denmark
6. Department of Haematology, University Hospital Rigshospitalet , Copenhagen, Denmark