Some of these factors, along with PaO2/FiO2 index, the incidence of acute kidney injury (AKIN), co-infections, APACHE-II score, IFN-γ, IL-15, and CCL5, also contributed to differentiate the entire COVID-19 cohort from pandemic influenza A(H1N1) subjects (Supplemental Figure 4). This evidence concerns the gene IL15 and COVID-19.