While reduction in plasminogen levels in the blood may represent a biomarker for disease severity, improved oxygenation was demonstrated after plasminogen inhalation in a case series of 13 COVID-19 patients.22, 23Indeed, in our cohort, 47% of patients with COVID-19, and 20% of patients without COVID-19 displayed elevated plasminogen levels. This evidence concerns the gene PLG and COVID-19.