However, in our study, although the levels of glutathione (GSH) were not found to be different between COVID-19-positive patients and healthy controls, we observed increased activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and the increases were more significant in patients with severe symptoms. Here, SOD1 is linked to COVID-19.