[1] Univ Bern, Inst Social & Prevent Med, Bern, Switzerland
[2] Univ Bern, Univ Hosp Bern, Div Paediat Resp Med & Allergol, Dept Paediat,Inselspital, Bern, Switzerland
[3] Univ Childrens Hosp Zurich, Paediat Pulmonol, Zurich, Switzerland
[4] Univ Lausanne, Univ Lausanne Hosp, Dept Resp Med, Lausanne, Switzerland
[5] Univ Bern, Dept BioMed Res, Bern, Switzerland