PF4 and COVID-19: Nevertheless, of relevance to the current review, beside direct platelet activation resulting from direct interaction of SARS-CoV-2 spike protein with platelet receptors [15], ‘HIT-like’ events may occur in a small proportion of patients with COVID-19, and there have been several reports of anti-PF4 antibodies in COVID-19 patients, as recently reviewed by some of us [20].