[1] Univ Antwerp, Dept Epidemiol & Community Med, B-2610 Antwerp, Belgium
[2] Univ Antwerp, Dept Immunol, B-2610 Antwerp, Belgium
[3] Univ Antwerp Hosp, Dept Paediat, Antwerp, Belgium
[4] Erasmus MC, Dept Otorhinolaryngol Head & Neck Surg, Rotterdam, Netherlands