Since nAbs as well as total IgG are reported to be a correlate of protective immunity against symptomatic COVID-19 (27), we next assessed a surrogate of nAb activity using the MSD-platform ACE2 inhibition assay (28), which is well correlated with live virus neutralisation assays (24, 26, 29, 30). The gene discussed is ACE2; the disease is COVID-19.