CTSL and COVID-19: Regarding the influence of CTSL and the comparison of the mean values in the separated groups according to the severity of COVID-19 and the correlation analysis, a positive relationship between CTSL, total IgA (p = 0.005, r = 0.437) and IL-28A was established (p = 0.013, r = 0.592) (Table 1 and Table 2; Figure 2E,F).