COVID-19 results in increased levels of plasma cytokines, including interleukin-6 (IL-6), interleukin-1β (IL-1β), interleukin-7 (IL-7), interleukin-8 (IL-8), interleukin-9 (IL-9), interleukin-10 (IL-10), granulocyte colony stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-γ (IFN-γ), tumor necrosis factor (TNF-α) and vascular endothelial growth factor A (VEGFA). This evidence concerns the gene IL9 and COVID-19.