Received: 27 September 2019
Accepted: 30 May 2020
First Online: 8 June 2020
Ethics approval and consent to participate
: This study retrospectively analyses laboratory reports collected as part of routine national surveillance for health protection purposes, and as such it is classified as ‘usual practice’ by the NHS Health Research Authority [CitationRef removed]. Therefore, ethical approval and research ethics committee review was not required, and informed consent was not obtained from participants in advance.
: Not applicable.
: The authors declare that they have no competing interests.