The blockage of C5a-C5aR1 axis limits the infiltration of myeloid cells in damaged organs, hampers the production of pro-thrombotic factors by immune cells, platelets, and ECs, as well as prevents the excessive lung inflammation and endotheliitis associated with acute respiratory distress syndrome in patients with COVID-19 (58, 64, 222). The gene discussed is C5; the disease is COVID-19.