Our results indicated that there were significantly more severe stage-specific monocytes (cluster 9), plasma B cells (cluster 11), and proliferating CD8+ T cells (cluster 12) in severe COVID-19 patients than in healthy controls (Supplementary Fig. 8a-c, P < 0.05, Student’s t test), which are findings that are consistent with our main conclusions. This evidence concerns the gene CD8A and COVID-19.