1. Hospital for Children and Adolescents and Folkhälsan Research Center, University of Helsinki, Helsinki, Finland;
2. Department of Pediatrics, Tampere University Hospital, Tampere, Finland;
3. Department of Pediatrics, University of Turku, Turku, Finland;
4. Department of Pediatrics, University of Oulu, Oulu, Finland;
5. Department of Clinical Microbiology, University of Kuopio, Kuopio, Finland;
6. Immunogenetics Laboratory, University of Turku, Turku, Finland.