This model reinforced the importance of myeloid, NK cell, Th1, and platelet activation in classifying patients with Delta phase COVID-19, with hospitalization during this period driven by higher concentrations of sCD40L, IL-6, IL-15, IL-18, CCL4, and CCL3, as well as compensatory anti-inflammatory, Th2-related mediators (IL-10, IL-1Ra, IL-5), and those reflective of pro-fibrotic epithelial regeneration/repair (TGF-α) (Fig. 4b, c). Here, IL15 is linked to COVID-19.