Received: 9 February 2020
Accepted: 13 May 2020
First Online: 2 July 2020
Ethics approval and consent to participate
: The serological study (Pienter2) was approved by the Medical Ethics Testing Committee of the foundation of therapeutic evaluation of medicines (METC-STEG) in Almere, the Netherlands (clinical trial number: ISRCTN 20164309). All participants or their legal representatives had given written informed consent. The retrospective birth cohort study (CROCUS) was approved by the ethical committee of the Leiden University Medical Center in Leiden and is registered in the Dutch Trial Register under NTR3582.
: Not applicable.
: The authors declare that they have no competing interests.