Both neutrophils and C5a (a surrogate marker of complement activation) are raised in the severe phenotype in the CASCADE study (Figures 3, 4), and they show a positive correlation in the heatmaps (Figure 8); therefore, the severity of inflammation in COVID-19 patients due to complement activation might be attenuated by the release of neutrophil elastase in COVID-19. Here, C5 is linked to COVID-19.