Knowing that intensity of the immune response is a critical factor during COVID-19 [18], considering the clinical need to better comprehend the pathophysiological basis of LC, and with the aim to ascertain relevant biomarker(s) that might aid in the diagnosis and objective monitoring of the disease, we compared the transcript levels of IFN-α, IFN-β, ISG15 and ISG56 in PBMC from a subgroup of previously SARS-CoV-2 infected participants (n = 24), stratified as LC (n = 16) and NLC (n = 8). This evidence concerns the gene ISG15 and COVID-19.