Funding for this research was provided by:
Helse Nord RHF (HNF 1450-19)
Grete Harbitz foundation
Received: 2 May 2019
Accepted: 12 June 2019
First Online: 15 July 2019
Ethics approval and consent to participate
: Approval from medical research ethical committees and data protection authorities was granted according to the regulations of each participating country, in Norway from Regional Committee for Medical and Health Research Ethics NORD, number 53/96<i>.</i> Oral informed assent was obtained from all children. Written informed consent was obtained from parents of children aged < 16 years and from the children if aged ≥16 years of age.
: Not applicable.
: The authors declare that they have no competing interests.