In addition, we found that IFNG, CCL2, and CXCL10 cytokines, which were previously described as molecular markers in severely ill patients (Sette and Crotty, 2021; Vabret et al., 2020), displayed low expression in our severe COVID-19 patients in comparison with mildly ill patients during the progression of disease (Figure 1D). Here, CCL2 is linked to COVID-19.