Liu et al. reviewed 55 studies that compared patients with severe and non-severe COVID-19 and found that the serum levels of IL-2, IL-2R, IL-4, IL-6, IL-8, IL-10, and TNF-α were significantly upregulated in patients with severe disease, with a sharp difference for IL-6 and IL-10.12 Here, IL6 is linked to COVID-19.