Univariate and multivariate logistic regression analysis for the studied parameters affecting severe from mild COVID-19 infection showed that old age, male gender, non-vaccination, HLA-DQ rs7453920AG+AA, HLA-DPrs3077GA+GG, and IFNλ4 rs73555604CT+CC genotypes are independent risk factors for the deterioration of COVID-19 manifestations (Figures 1–3). The gene discussed is IFNL4; the disease is COVID-19.