Since the end of 2019, Egypt and the whole world have been suffering from the Coronavirus Disease 2019 (COVID-19) pandemic, which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). According to the World Health Organization (WHO), since the emergence of this new pandemic, there have been more than 97 million confirmed cases of COVID-19 patients and two million death globally; around 160 thousand of these cases are in Egypt.

Recent clinical investigations found a high incidence of thrombotic complications in these patients, even with the standard anticoagulant thromboprophylaxis.Coronavirus disease 2019 (COVID-19) causes a hypercoagulable state. Among the pathological sequel of COVID-19 infection, is the presence of a micro-thrombi in the pulmonary circulation which was shown in several autopsy studies. This thrombosis is believed to contribute to gas exchange impairment among patients with COVID-19 infection.

Some observational studies have shown anticoagulation benefits with reduced mortality, mainly in patients requiring mechanical ventilation. However, these findings remain uncertain and need to be validated in further studies.

This study is performed to evaluate whether therapeutic anticoagulation could improve COVID-19 patients' clinical outcomes compared to prophylactic anticoagulation in terms of improving gas exchange, reducing the need to maintain mechanical ventilation, shortening hospital admission period and mortality rate as well as recovering D-dimmer levels to its normal values.

Inclusion Criteria:

1. Age 18 to 65 years..
2. COVID-19 hospitalized patients with pneumonia proved by chest X-ray or CT scan.
3. Confirmed infection with COVID-19 virus using RT-PCR or strongly suspected to be infected with pending confirmation studies.
4. Prothrombin time/international normalized ratio (INR)<1.5; activated partial thromboplastin time (aPTT)/ratio<1.5, and platelet count greater than 100,000/mm3.

Exclusion Criteria:

1. Age greater than 85 years-old
2. Creatinine clearance (CrCl)<10ml/min.
3. Severe circulatory shock with a dose of norepinephrine higher than 1.0 μg/kg/min.
4. Pregnant women.
5. Recent major surgery or severe trauma in the last 3 weeks or recent hemorrhagic stroke in the last 3 months.
6. Active bleeding, blood dyscrasia such as hemophilia and Von Willebrand factor deficiency.

The current research is including moderate and severe SARS-COV-2 patients receiving the same background treatment for 5 days, following an Institutional protocol for standard of care: hydroxychloroquine 400 mg daily, lopinavir/ritonavir 400/100 mg twice daily or/and remdisivir 200 mg LD then 100 once daily as a maintenance dose and anti-coagulation prophylaxis with enoxaparin subcutaneously once a day if D-dimmer between 500-1000 or enoxaparin therapeutic subcutaneously twice daily if D-dimmer >1000.