Funding for this research was provided by:
Wellcome Trust (093564/Z/10/Z)
Medical Research Council (MR/K006525/1)
Received: 25 September 2018
Accepted: 20 June 2019
First Online: 2 September 2019
Ethics approval and consent to participate
: Ethical approval and consent to participate were not required as the study data is based on fully anonymised data. Approval was obtained instead from the independent Information Governance Review Panel (IGRP) that includes members from the NHS National Research Ethics Service, the British Medical Association, Caldicott Guardians from Public Health Wales NHS Trust and NHS Wales Informatics Service, and members of the public.
: Not applicable.
: Keir Lewis reports personal fees from Chiesi, Pfizer and Astra Zeneca for speaker fees and advisory during the conduct of the study. All other authors declare no competing interests.