COVID-19 and Thrombosis

Eyes Open to COVID-19 and Thrombosis

COVID-19 and Thrombosis

COVID-19 infection can cause mild flu-like symptoms to causing pneumonia where those affected can get very breathless and require additional oxygen, even mechanical ventilation. COVID-19 pneumonia causes an inflammatory response that increases clotting factors in the blood, making blood clots in veins and arteries more likely. The risk of VTE is especially high in those with COVID-19 pneumonia.

Research has now shows that small doses of anticoagulants reduce the risk of hospital associated VTE in those with COVID-19 pneumonia and larger doses help improve recovery in those who only need supplementary oxygen.

The treatment of blood clots acquired during or after a hospital stay with COVID-19 pneumonia is the same as standard care in those who don’t have COVID-19.

What is COVID-19 Vaccine Immune Thrombosis and Thrombocytopenia (VITT)?

VITT is a very rare occurrence after certain COVID-19 vaccines. Symptoms start five or more days after the Astra- Zeneca or Johnson & Johnson COVID-19 vaccines and blood clots usually occur at unusual sites in the body. Cerebral venous sinus thrombosis occurs in 50 percent and can cause headaches which are unusually severe and persistent and may be worse on lying down or bending forward. The headache may occur with changes in vision, feeling or being sick. Fits (seizures) can occur, or weakness on one side of the body or a drop in consciousness.

Other symptoms can include:

  • Persistent abdominal (tummy) pain
  • Blood in the stools
  • Chest pain, shortness of breath
  • Leg pain and/or swelling

COVID-19 and Thrombosis FAQs

Yes. The COVID-19 vaccine is given as an intramuscular injection into your upper arm. Individuals receiving direct oral anticoagulant (apixaban, dabigatran, edoxaban & rivaroxaban) or warfarin in therapeutic INR range or on full dose heparin or fondaparinux injections can all receive the COVID-19 vaccination.

  • There is a risk of bruising at the injection site, but we do not anticipate any serious effects related to anticoagulation
  • We suggest that after the injection prolonged pressure (at least 5 minutes) should be applied to the injection site to reduce bruising
  • Patients on warfarin with supra-therapeutic INR should wait until their INR is <4.0
  • We encourage patients to have vaccinations and should not be avoided on the basis of being on anticoagulation

No, having a previous blood clot does not increase your risk of contracting COVID-19 or having more problems with the infection.

Taking anticoagulants does not increase your risk of getting COVID-19, however some people taking anticoagulants might have other health issues that increase their risk for getting COVID-19. For example, people with cancer who have had a blood clot might be on anticoagulants but are also taking cancer treatment drugs that lower their immunity. The low immunity might increase the risk of COVID-19 pneumonia but the anticoagulant treatments do not add to the risk.

If you are already on an anticoagulant(s) and get COVID-19, you should continue taking your medication as instructed by your healthcare professional. Keep taking it regularly, and don’t skip any doses.[1]

WHY? In severe COVID-19 infection, anticoagulation may be a helpful preventative measure if you acquire COVID-19.[2]

Please seek medical advice to see if you qualify for anti-viral treatments that are used in those at high risk of developing COVID-19 pneumonia

If you are diagnosed with COVID-19, and previously had a blood clot, make sure you tell your healthcare provider immediately. Let them know if you are currently taking an anticoagulant and ask for a venous thromboembolism (VTE) risk assessment if you are admitted to a hospital. [3]

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COVID-19 and Thrombosis Resources

World Thrombosis Day and its partners have developed resources for patient and healthcare professionals around COVID-19 and blood clots.

Page references:

[1] Prof. Beverley Hunt Interview in Thrombosis UK Video;

[2] Clinical Guidance on the Diagnosis, Prevention and Treatment of Venous Thromboembolism in Hospitalized Patients with COVID-19,” published on 5/27/20 in the Journal of Thrombosis and Haemostasis (JTH)


[4] “Clinical Guidance on the Diagnosis, Prevention and Treatment of Venous Thromboembolism in Hospitalized Patients with COVID-19,” published on 5/27/20 in the Journal of Thrombosis and Haemostasis (JTH)