Tarke et al. demonstrated that CD4+ and CD8+ T cell responses in convalescent COVID-19 subjects or COVID-19 mRNA vaccines (BNT162b2 and mRNA-1273) were not substantially affected by mutations found in the B.1.1.7, B.1.351, P.1, and CAL.20C variants [156]. Here, CD4 is linked to COVID-19.