IL9 and COVID-19: A dysregulation in cytokine content has been linked to T cell exhaustion in patients who recovered from COVID-19 (n = 39) (32), with higher levels of IL-1β, IL-1RA, IL-7, IL-8, IL-10, IFN-γ, and MIP-1α, and a decrease in IL-9, CCL11, MIP-1β, and RANTES, as compared with healthy controls (n = 43) (32).