CCL2 and COVID-19: Given the above research, we focused on the following biomarkers—CXCL8, CCL2, and C-C motif chemokine receptor 1 (CCR1) expressions, as well as serum concentrations of CXCL8, C-X-C motif chemokine ligand 10 (CXCL10/IP-10), CCL2, and CCL3, as they appear to contribute to the pathogenesis of severe COVID-19.