On hospital admission, COVID-19 patients showed significantly higher plasma levels of MMP-9 and TIMP-1 as well as a higher MMP-9/TIMP-1 ratio compared to HD (p < 0.0001, p < 0.0001 and p = 0.0299, respectively) (Figure 1A, Figure 1B and Figure 1C, respectively) (Table 2). This evidence concerns the gene MMP9 and COVID-19.