To assess the contribution of neutrophils in COVID-19 disease, we measured the neutrophil activation markers calprotectin (S100A8/A9), and NETs (MPO-DNA and NE-DNA complexes) at baseline in plasma samples from COVID-19 patients stratified based on disease severity (mild and moderate/severe disease) and in healthy controls (HCs). The gene discussed is MPO; the disease is COVID-19.