IFIH1 and COVID-19: Subsequent studies on peripheral blood mononuclear cells (PBMCs) from acute and convalescent COVID-19 subjects showed that the induction of IFIH1 positively correlated with increased type 1 IFN activity, IFN stimulated gene 15 positive (ISG15+) CD8+ cytotoxic T cell signature, and IFN response, i.