The result also indicated that the methylation level of the interferon type I pathway-related gene RSAD2 (cg10549986) for COVID-19 patients was negatively correlated to the severity of COVID-19, and the expression of RSAD2 is reported to have reached the highest level in the early stage compared with the late stage of COVID-19 (Zhang C. et al., 2021). This evidence concerns the gene RSAD2 and COVID-19.