1. Center for Child Health Research; Tampere University and University Hospital; Tampere Finland
2. Department of Pediatrics; Seinäjoki Central Hospital; Seinäjoki Finland
3. Tampere University Hospital; Tampere Finland
4. Department of Medical Microbiology and Immunology; Turku University; Turku Finland
5. Department of Infectious Disease Surveillance and Control; National Institute for Health and Welfare; Turku Finland