Funding for this research was provided by:
National Institute for Health Research (IS-BRC-1215-20008)
National Institutes of Health (UL1 RR025780)
Received: 4 November 2018
Accepted: 23 May 2019
First Online: 7 June 2019
Ethics approval and consent to participate
: The study was approved by the Central University Research Ethics Committee of the University of Oxford (Reference: R55722/RE001). All participants provided informed consent.
: Not applicable.
: The authors declare that they have no competing interests.