Inclusion Criteria:

• Patients ≥ 18 years of age.
• Willing and able to provide (possibly through a substitute decision maker) informed consent.
• Require hospitalization anticipated to last ≥ 72 hours for microbiologically-confirmed COVID-19.
• Enrolled < 72 hours of hospital admission or of COVID-19 confirmation.

Exclusion Criteria:

• Patients < 18 years of age.
• Requirement for chronic mechanical ventilation via tracheostomy prior to hospitalization.
• Patients for whom the intent is to not use pharmacologic thromboprophylaxis.
• Active bleeding.
• Risk factors for bleeding, including:
  • intracranial surgery or stroke within 3 months;
  • history of intracerebral arteriovenous malformation;
  • cerebral aneurysm or mass lesions of the central nervous system;
  • intracranial malignancy;
  • history of intracranial bleeding;
  • history of bleeding diatheses (e.g., hemophilia);
  • history of gastrointestinal bleeding within previous 3 months;
  • thrombolysis within the previous 7 days;
  • presence of an epidural or spinal catheter;
  • recent major surgery 200 mmHg, dBP > 120 mmHg);
  • other physician-perceived contraindications to anticoagulation.
• Platelet count 2.0, or baseline aPTT > 50.
• Hemoglobin < 80 g/L (to minimize the likelihood of requiring red blood cell transfusion if potential bleeding were to occur).
• Acute or subacute bacterial endocarditis.
• History of heparin induced thrombocytopenia (HIT) or other heparin allergy including hypersensitivity.
• Current use of dual antiplatelet therapy.
• Patients with an independent indication for therapeutic anticoagulation.
• Patients in whom imminent demise is anticipated and there is no commitment to active ongoing intervention.
• Anticipated transfer to another hospital that is not a study site within 72 hours.
• Enrollment in other trials related to anti-coagulation or antiplatelet therapy