C5 and COVID-19: To determine whether critical COVID-19 patients have high levels of the complement inflammatory mediators anaphylatoxins C3a and C5a, systemic levels of complement (anaphylatoxins) C3a, a product of C3 cleavage, and C5a, a product of C5 cleavage, were measured in samples from patients with confirmed SARS-CoV-2 infection (26 critical and 27 mild), and 17 healthy groups.