Received: 22 October 2019
Accepted: 7 May 2020
First Online: 26 June 2020
Ethics approval and consent to participate
: Not applicable.
: NIBSC is a centre of the UK’s Medicine and Healthcare product Regulatory Agency and is a non-profit institute which generates global reference reagents for public health. Reagents generated by NIBSC will be published here will be distributed on a cost-recovery basis. We have no other competing interests to declare.