1. Department of Pediatrics and Adolescent Medicine, University of Turku, Turku, Finland.
2. Department of Pediatrics and Adolescent Medicine, Turku University Hospital, Turku, Finland.
3. City of Turku Welfare Division, Primary Healthcare Services, Turku, Finland.
4. Department of Otorhinolaryngology–Head and Neck Surgery, University of Turku, Turku, Finland.
5. Department of Otorhinolaryngology–Head and Neck Surgery, Turku University Hospital, Turku, Finland.
6. Department of Clinical Microbiology, Turku University Hospital, Turku, Finland.
7. Department of Biostatistics, University of Turku, Turku, Finland.