COVID‐19 patients in cluster 2 had fewer infiltrating B cells, T cells, and natural killer (NK) cells, which was consistent with the fact that severe forms of COVID‐19 are characterised by a marked decrease in the total number of peripheral blood lymphocytes, including both CD4+ and CD8+ T cells, B lymphocytes, and NK cells31 (Figure 5C). This evidence concerns the gene CD8A and COVID-19.