Coronavirus disease 2019 (COVID-19), the disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has resulted in a global pandemic and a disruptive health crisis. COVID-19–related morbidity and mortality have been attributed to an exaggerated immune response. The role of complement activation and its contribution to illness severity is being increasingly recognized. Here, we summarize current knowledge about the interaction of coronaviruses with the complement system. We posit that (a) coronaviruses activate multiple complement pathways; (b) severe COVID-19 clinical features often resemble complementopathies; (c) the combined effects of complement activation, dysregulated neutrophilia, endothelial injury, and hypercoagulability appear to be intertwined to drive the severe features of COVID-19; (d) a subset of patients with COVID-19 may have a genetic predisposition associated with complement dysregulation; and (e) these observations create a basis for clinical trials of complement inhibitors in life-threatening illness.

Evidence suggests that immunogenicity to mRNA-based SARS-CoV-2 vaccination in immunosuppressed patients may be reduced. This study assessed the response to 2 doses of mRNA-based SARS-CoV-2 vaccine ... Visual Effect of Immunosuppression on Immunogenicity of mRNA SARS-CoV-2 Vaccines. Evidence suggests that immunogenicity to mRNA-based SARS-CoV-2 vaccination in immunosuppressed patients ma... Background: Patients with chronic inflammatory disease (CID) treated with immunosuppressive medications have increased risk for severe COVID-19. Although mRNA-based SARS-CoV-2 vaccination provides ...

Increased complement activation is observed in COVID-19 compared with non-COVID respiratory illness and is a key marker of organ failure.