On the other hand, we found that expression of three ISGs, namely, IRF3, ISG15, and IFI6, were significantly higher in convalescent COVID-19 individuals after stimulation with IFN-β, IFN-α/β, and IFN-β, respectively (Figure 3G), indicating that the degree of induction by type I IFNs is higher for some of the IFN regulated genes in convalescent individuals compared to healthy volunteers. Here, ISG15 is linked to COVID-19.