Notably, while the level of IFN-β was decreased markedly by secondary SARS-CoV-2 infection at 7 dpi in the IAV + SARS-CoV-2 coinfection group, the opposite patterns were observed in the SARS-CoV-2 + IAV group from 5 to 10 dpi (Fig. 4D). This evidence concerns the gene IFNB1 and COVID-19.