C5AR1 and COVID-19: When we measured circulating levels of C5a and sC5b-9, we found that COVID-19 patients had significantly increased levels of C5a and sC5b-9 compared to healthy subjects (C5a: 41.4 ± 20.6 vs 7.6 ± 2.2 ng/ml, p-value<0.0001; sC5b9: 1137 ± 432 vs 205 ± 59 ng/ml, p-value<0.0001).