Serum S100A8/A9 levels were quantifiedas previously described and compared with levels in HC samples.26 The averages of serum S100A8/A9 concentrationsin COVID-19 patients (15580.7 ng/mL) were 9-fold higher compared toHCs (1662.6 ng/mL) (Figure 1A). Here, S100A8 is linked to COVID-19.