A significant increasing trend of IL-1β, IL-1ra, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12(p70), IL-15, IL-17, FGF-b, G-CSF, GM-CSF, IFN-γ, IP-10, MCP-1, MIP-1α, PDGF, TNF-α, and VEGF was observed in the three groups (Controls ≤ Mild COVID-19 ≤ Severe COVID-19) (Table 1, Fig. 1). Here, IL15 is linked to COVID-19.