To investigate whether a biosafety level (BSL) 2 approved pseudotyped lentivirus expressing SARS-CoV-2 S glycoprotein tagged with a luciferase reporter could detect neutralising antibodies, we performed an initial screen at 1:1000 dilution using sera from 25 convalescent COVID-19 patients and from 13 SARS patients recalled in January–February 2020 as controls (Fig. 1a). Here, ART4 is linked to severe acute respiratory syndrome.