C5AR1 and COVID-19: The contribution of complement activation and both lytic and sublytic C5b-9 effects on endothelial cells to the pathological vascular changes seen in the brains of patients with COVID-19 is now considered very important and led to clinical trials using C5 blockade with monoclonal antibodies or drugs targeting C5, C5a, or C5aR1 are still ongoing (33).