distinguished COVID-19 patients from healthy controls (AUC = 0.975). Plasma monosialodihexosyl gangliosides (GM3s) were negatively correlated with CD4+ T cell count in COVID-19 patients, and GM3-enriched exosomes were positively correlated with disease severity. These observations suggest that GM3-enriched exosomes may participate in pathological processes associated with COVID-19 progression.