Funding for this research was provided by:
University of Oslo
Accepted: 20 August 2021
First Online: 18 September 2021
: This study was prospectively reviewed and approved by a Regional Committee for medical and health research ethics and all procedures were in accordance with the ethical standards of the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all parents of children below 16 years of age and from all participants ≥ 16 years of age.
: We have no conflict of interest.