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Dr Malik comments on the Astra-Zeneca COVID 19 vaccine and Cerebral Venous Sinus Thrombosis issue


A thrombosis is a clot forming. It can occur in arteries, as in a heart attack or stroke, or in the veins as in Deep Vein Thrombosis (DVT) or Pulmonary Embolism (PE).
Cerebral venous sinus thrombosis (CVST) is a clot forming inside the brain-it is rare. 5 in 1 million people each year were diagnosed with it pre COVID 1

It accounts for a tiny proportion (0.5%) of all strokes. It is an important cause of stroke in younger patients. A clot forming here leads to a rise in pressure inside the skull, compressing the brain.

Dr Iqbal Malik, Consultant Cardiologist at OneWelbeck Heart Health, investigates.

What are the symptoms of CVST?

  • a new onset of severe or persistent headache, blurred vision, confusion or seizures- suggesting CVST
  • develop shortness of breath, chest pain, leg swelling or persistent abdominal pain, suggesting clots elsewhere
  • unusual skin bruising or pinpoint round spots beyond the injection site- suggesting low platelets

What Causes CVST?

Infections, especially close to the face and ears (eg, mastoiditis, otitis, meningitis) may lead to spread to the venous sinuses and clots forming in the brain, resulting in focal neurologic deficits, seizures, coma, and death. However, CVST is now primarily recognized as a non-infectious disease.

Risk factors include those that cause clots in the legs (DVT) such as cancer, obesity, genetic thrombophilia, trauma, infection and prior surgery. However, the most common acquired risk factors for CVST are oral contraceptive use and pregnancy, which explains why it is 3 times more likely to occur in young and middle-aged women.

COVID-19 Vaccines and CVST

The latest data (as of 7th April 2021) suggested a rate of CVST of 4 per million Astra-Zeneca vaccine doses. Thus the rate is similar to those published in previous years. It is reported more in women, but it’s predicted more women have had the vaccine as they make up a large part of the healthcare workforce- where vaccines have been targeted.
Some individuals have low platelets which is unusual and may be mediated by an unforeseen immune response.

Is the Astra-Zeneca vaccine safe?

The short answer is YES.
No medicine or vaccine is 100% safe. But the AZ vaccine does provide protection against a common and deadly disease but may have an association with a very rare clotting condition. An association is not causation. It may yet be the case that this observation was nothing to do with the vaccine.

The UK MHRA 2 has issued guidance on what to do if you are worried. A simple guide to vaccines from Public Health England is also available here.

If you are worried, please get in contact with your doctor or GP.




Written by Dr Iqbal Malik, Medical Director and Consultant Cardiologist at OneWelbeck Heart Health, specialising in coronary artery disease and structural heart disease including PFO, ASD and the TAVI procedure.