MMP9 and COVID-19: Finally, possible correlations among C-RAF, H-RAS, MAPK1, MAPK2, pERK and iERK vs. other COVID-19-related biomarkers (VEGF, HIF, TNFα, vitamin D, hepcidin, ICAM-1, VCAM, MMP9, IL-6) were evaluated: C-RAF with age (p = 0.047, S = 0.309) and plasma VEGF (p = 0.026, S = 0.729); MAPK1 and HIF (p = 0.050, S = 0.812); iERK and HIF (p = 0.008, S = 0.928); pERK with TNFα (p = 0.012, S = −0.365) and vitamin D levels at baseline (p = 0.024, S = −0.643).