Received: 25 August 2020
Accepted: 2 November 2020
First Online: 10 November 2020
Ethics approval and consent to participate
: This study is considered enhanced routine surveillance of vaccination coverage. The register part of the study falls under the general agreement for non-interventional database studies between the Danish Data Protection Agency and Statens Serum Institut, reference number 2008-54-0474. Ethics approval of health science questionnaire surveys and interview surveys, that do not include human biological material, by the National Scientific Ethics committee is not necessary according to Danish legislation (Committee Act § 14, sction 2).All participants were under 16 years, and informed consent were obtained from the parents/guardians. For parents/guardians participating by answering the written questionnaire, information on the study was giving in the invitation, and the option to opt out was clear. Consent was giving by accepting participation. Same information and options were giving verbally to parents/guardians reached by telephone.
: Not applicable.
: Ida Glode Helmuth has conducted a PhD study on varicella epidemiology in Denmark that received an unrestricted research grant from GSK to her employer at Rigshospitalet. All other authors have no competing interest to declare.