IFNG and COVID-19: A sufficient level of vitamin D is required for a normal IFN gamma-induced antimicrobial peptide expression in macrophages [43], yet a dysregulated or delayed IFN gamma response will allow viral immune evasion [44] and severe forms of COVID-19 after IFN gamma upregulation during the later phase with enhanced cytokine production and hyper-inflammation, thus leading to severe disease [45].