CD4 and COVID-19: However, it is not yet known whether these cross-reactive memory CD4+ and CD8+ T cells: (i) preferentially cross-recognize the alpha CCCs (i.e., α-CCC-229E and α-CCC-NL63) or the beta CCCs (i.e., β-CCC-HKU1 and β-CCC-OC43); and (ii) the antigen-specificity, frequency, phenotype, and function of the cross-reactive memory CD4+ and CD8+ T cells associated with protection against COVID-19 severity in unvaccinated asymptomatic patients.