For CCL22 mRNA, there were no significant differences in expression among the serial specimens collected from COVID-19 patients; however, CCL22 mRNA expression (IQR) was statistically significantly lower in patients with severe COVID-19 versus those with mild COVID-19 as shown in Figure 5 and Supplementary Table 8 (first specimen: 1779.3 × 10−6 (746.9–3514.7) vs 4914.2 × 10−6 (1612.3–9114.2), p < 0.001; second specimen: 1350.3 × 10−6 (334.8–2668.2) vs 2812.3 × 10−6 (1421.5–5892.1), p = 0.003; third specimen: 1156.1 × 10−6 (384.0–3435.2) vs 3814.3 × 10−6 (881.4–5240.0), p = 0.032). Here, CCL22 is linked to COVID-19.