CD40LG and susceptibility to pneumonia measurement: There were significant differences in age (34 vs. 43 years; p < 0.001), SARS-CoV-2 IgM titer (0.3 vs. 0.1 AU/ml; p = 0.002), SARS-CoV-2 IgG seropositive (84 vs. 44%; p < 0.001), and titer (82.8 vs. 3.3 AU/ml; p < 0.001), lymphocyte (1.36 vs. 0.87 × 10^9/L; p = 0.002) and platelet count (224 vs. 200 × 10^9/L; p = 0.04), fibrinogen (2.9 vs. 3.3 g/L; p < 0.001), and aspartate aminotransferase (27 vs. 29 U/L; p = 0.01) between the non-pneumonia (n = 115) and pneumonia (n = 46) groups.