On the basis of analysis of whole-genome sequencing (WGS) and whole -exome sequencing (WES) data on host individuals, critical illnesses can be correlated with genes involved in innate antiviral defense such as Interferon Alpha and Beta Receptor Subunit 2 (IFNAR2) and Oligoadenylate Synthetase (OAS), and the genes mediating the life-threatening late phage of COVID-19 such as Dipeptidyl Peptidase 9 (DPP9), Tyrosine Kinase 2 (TYK2), and Chemokine (C-C motif) Ligand 2 (CCL2). This evidence concerns the gene TYK2 and COVID-19.