ISG15 and COVID-19: As a consequent to activation of JAK-STAT pathway, the mRNA and protein levels of ISGs such as MX-1 and ISG-15 were also elevated in saliva of VitD treated COVID-19 patients compared to the controls (Fig. 3Q–V, 1.40 log FC increase of MX-1 mRNA, P < 0.0001; and 6.55 log FC increase of ISG-15 mRNA, P < 0.0001).