IFNK and COVID-19: We have previously tested this concept in SARS-CoV-2 infected patients during the first wave of the COVID-19 outbreak in 2020, and the results showed that the combination of TFF2 and human IFN kappa, one of the type I IFNs, is a highly safe and effective therapeutic for COVID-19 (Fu et al., 2020a; Fu et al., 2020b).