IL15 and COVID-19: In particular, clusters 16, 22, and 27, which were enriched in moderate COVID-19, displayed a positive correlation with several molecules of type 1 response (CXCL9, CXCL10, and IL-15), antiviral response (interferon regulatory factor 9 [IRF9], IL-12p70, and interferon-ɣ [IFNɣ]) and adaptive immunity (B cell activating factor [BAFF] and IL-2) (Fig. 3D).