PF4 and COVID-19: Recently, the C5a–C5aR1 axis was suggested to be an important marker of inflammation associated with COVID-19.33Interestingly, the platelet C5aR1 has been recognized as an important player in the complex pathophysiology of SARS-CoV-2 infection.34Thus, evaluating the C5aR1–CXCL4 axis in this context may improve our understanding of disease mechanisms and provide new treatment options for COVID-19 and other diseases featuring thromboinflammation and complement involvement.