CD69 and COVID-19: To investigate whether these public dominant TCRα clonotypes are associated with COVID-19 disease severity, we utilised two publicly available datasets of SARS-CoV-2-reactive CD4+ T cells with available TCR information, identified based on the upregulation of CD154/CD137/CD69 expression following peptide pool stimulation, for 52 COVID-19 patients29,37 (Supplementary Table 2).