In several previously published studies, the incidence of Acute Ischemic Stroke ranged from 0.9% to 2.7% in those with COVID-19, … 

One of the studies calculated a more than sevenfold greater risk of Acute Ischemic Stroke among patients with COVID-19 compared with patients with influenza…
… three mechanisms that may be contributing to the increased risk for Acute Ischemic Stroke accompanying COVID-19: binding of the virus to the ACE2 receptor on blood vessel walls causing vasculitis, cardioembolism, or paradoxical embolism, and the well-known hypercoagulability state that occurs with COVID-19.

The authors  reasoned that if cardioembolism or paradoxical embolism were the cause of the strokes, anticoagulation should have a preventive effect. If platelet hyperaggregability played a role, antiplatelet agents could be beneficial.

The aim of the study was to investigate the role of thromboprophylaxis in the primary prevention of cerebrovascular events among patients with COVID-19. The conclusions of the study were that  anticoagulation and/or antiplatelet therapy with a variety of agents did not prevent acute ischemic stroke in elderly patients with COVID-19 and comorbidities.