In accordance with the cross-study hierarchical clustering, CCA revealed a strong association between several cytokine/chemotaxis-related genes (e.g., CXCL8, CEACAMs [1/6/8], IL1RAP, IL1R1, IL1B, NFKB1) with those involved in neutrophil-mediated immune responses (e.g., CTSG, ELANE, MMP8, TCN1) in both COVID-19 patients and controls (Figure 3A,B). This evidence concerns the gene CTSG and COVID-19.