However, determination of T cell receptor excision circles of PB T cells (TRECs), which negatively correlated with the increased age of our patients and correlated with the numbers of both CD3+CD4+ and CD3+CD8+ RTE did not indicate problems with thymic output in COVID‐19 convalescent patients with a mild disease course when compared to healthy control subjects (Figure 2; Figures S3). This evidence concerns the gene CD4 and COVID-19.