Study title

The new SARS-CoV-2 pandemic leads to coronavirus disease COVID-19 with consisting of respiratory failure, with substantial morbidity, and significant mortality. Over-activation of the innate immune response is postulated to trigger this detrimental process. The complement system is a key-player of innate immunity. Despite a few reports of local complement activation, there is lack of evidence that to which the degree ofa global systemic complement activation occurs early in COVID-19 patients, and if this activation is associated with respiratory failure. This study shows that a number of complement activation products areis systemically, consistently, and long-lastingly increased activated from admission and during the hospital stay in COVID-19 patients. Notably, the terminal sC5b-9 complement complex was associated with respiratory failure. Thus, complement inhibition is an attractive therapeutic approach for treatment of COVD-19 patients