In addition, the size effect analysis displayed moderate differences between mild and severe COVID-19 patients in the content of TNF (Cohen’s d = 0.428), IFNɣ (Cohen’s d = 0.424187), IL-2 (Cohen’s d = 0.544), and IL-17 (Cohen’s d = 0.528) (Figure 7 and Supplementary Figure SM1f–h). Here, IL2 is linked to COVID-19.