Funding for this research was provided by:
Norwegian Institute of Public Health (not applicable)
Received: 29 March 2020
Accepted: 23 March 2021
First Online: 7 April 2021
: The planning and conduct of the study conformed to the Declaration of Helsinki, as revised in 2013. The South-East Regional Committee for Medical Research Ethics approved the study (id. 2019/808). As part of the approval, exemption from consent to participate was waived based on the Health Research Act § 35, in accordance with §§ 15 (second section) and 28 (first section): notification of vaccination in the Norwegian Child Immunisation Programme is mandatory without asking for consent, and (iii) the benefit to the society is high.
: Not applicable.
: The authors declare that they have no competing interests.