GZMB and COVID-19: Immunoassay quantification of these proteases in serum indicate that within 48 h of admission, severe COVID-19 patients had significantly higher levels of neutrophil elastase (median 71.8 pg/mL versus 2.8 pg/mL; p > 0.001) (Figure 1A) and granzyme B (median 8.0 pg/mL versus 2.3 pg/mL; p = 0.006) (Figure 1B).