[1] Turku Univ Hosp, Dept Pediat, FIN-20520 Turku, Finland
[2] Univ Turku, Dept Virol, Turku, Finland
[3] Turku Univ Hosp, Dept Clin Physiol, FIN-20520 Turku, Finland
[4] Univ Turku, Dept Biostat, Turku, Finland
[5] Univ Helsinki Hosp, Skin & Allergy Hosp, Dept Allergol, Helsinki, Finland