We observed that CCR2 expression levels (5.28 ± 1.89) were upregulated in mild COVID-19 patients compared to healthy controls (1.9 ± 0.57; P < 0.01), but there was no difference was observed between severe COVID-19 patients (1.83 ± 0.43) and healthy controls (Fig. 2a). Here, CCR2 is linked to COVID-19.