C4B and cyclic hematopoiesis: The strength of the association between CH and severe Covid-19 was similar among patients with one CH mutation (OR = 1.78, 95% CI = 1.02–3.09, p = 0.04) and multiple CH mutations (OR = 1.97, 95% CI = 1.03–3.78, p = 0.04) (Supplementary Fig. 4).