Once the relationship between antibody detection and protective immunity is clarified, our results could also be used to stratify individuals by infection risk, identify individuals who would require vaccine boosters, and identify potential donors with high anti-S IgG (and thereby ability to inhibit ACE2 binding) for convalescent plasma, which has been shown to improve outcomes in critically ill COVID-19 patients (Chen et al., 2020a). This evidence concerns the gene ACE2 and infection.