IL9 and COVID-19: Profiling immune mediators in severe COVID-19 patients have revealed low concentrations of type I interferons (Hadjadj and others 2020; Masood and others 2021), and elevated levels of TNFα, IFNy, IL-1β, IL-1RA, IL-4, IL-6, IL-7, CXCL8, IL-9, IL-17A, CCL2, CCL3, CCL4, CCL5, CCL7, CCL8, CCL11, CXCL9, CXCL10, G-CSF, GM-CSF, PDGF, FGF, and VEGF (Chen and others 2020; Han and others 2020; Huang and others 2020; Kong and others 2020; Lucas and others 2020; Remy and others 2020; Wan and others 2020; Yang and others 2020; Zhu and others 2020b; Reynolds and others 2021; Sims and others 2021).