C3 and COVID-19: In a subgroup analysis comparing non-COVID-19 patients with SOFA Score ≥ 2 (n = 14) to patients with COVID-19 statistical analysis showed increased levels of complement component 3 (1.321 [± 0.2804] g/l vs. 1.51 [1.35–1.83] g/l; p = 0.031), 4 (0.2673 [± 0.0797] g/l vs. 0.3772 [± 0.1056] g/l; p = 0.0027) and 5a (0.159 [0.1175–0.203] pg/ml vs. 0.493 [0.139–0.583] pg/ml; p = 0.0378).