Intermediate or Prophylactic-Dose Anticoagulation for Venous or Arterial Thromboembolism in Severe COVID-19

Inclusion Criteria: * Confirmed diagnosis of COVID-19 by reverse transcription polymerase chain reaction (RT-PCR) * New admission to eligible CUIMC ICUs within 5 days * Transfer from nonparticipating to participating ICU is eligible if otherwise meets eligibility criteria. * Patients transferred between participating ICUs will maintain initial treatment assignment. * Patients not on therapeutic anticoagulation and who were already admitted to participating ICU within 5 days of trial initiation are additionally eligible. Exclusion Criteria: * Weight under 50kg * Contraindication to anticoagulation in the opinion of the treating clinician including * overt bleeding * platelet count \<50,000 * Bleeding Academic Research Consortium (BARC) major bleeding in the past 30 days * Gastrointestinal (GI) bleeding within 3 months * history of intracranial hemorrhage * Ischemic stroke within the past 2 weeks * craniotomy/major neurosurgery within the past 30 days * cardiothoracic surgery within the past 30 days * intra-abdominal surgery within 30 days prior to enrollment * Head or spinal trauma in the last months * History of uncorrected cerebral aneurysm or arteriovenous malformation (AVM) * Intracranial malignancy * Presence of an epidural or spinal catheter * Recent major surgery within the last 14 days * Decrease in hemoglobin \>3 g/dL over the last 24 hours * Allergic reaction to anticoagulants (e.g. Heparin Induced Thrombocytopenia) as documented in the electronic health records. Extracorporeal membrane oxygenation (ECMO) support or other mechanical circulatory support. * Severe chronic liver dysfunction (history of portosystemic hypertension (HTN), esophageal varices, or Child-Pugh class C or above or similar Model For End-Stage Liver Disease (MELD) scores), abnormality in liver function tests (aspartate aminotransferase (AST), alanine aminotransferase (ALT), bilirubin) 5 times greater than upper normal limit. * A history of congenital bleeding diatheses or anatomical anomaly that predisposes to hemorrhage (e.g. hemophilia, hereditary hemorrhagic telangiectasia) * Treating physician preference for therapeutic anticoagulation * Enrollment in other concurrent trials related to anticoagulant or antiplatelet therapy * Existing treatment with therapeutic anticoagulation during the previous 7 days of hospitalization prior to ICU admission (e.g. for venous thromboembolism (VTE), atrial fibrillation, mechanical valve, etc). * Do-not-resuscitate (DNR) /do-not-intubate (DNI) or comfort measures only (CMO) orders prior to randomization.