Thrombosis after AstraZeneca vaccination: Symptoms and treatment

As COVID-19 community infections increase again, people over the age of 50 are weighing the benefits of vaccination against the virus at the very rare risk of blood clotting induced by the AstraZeneca vaccine.

Since the first report of blood Coagulation after AstraZeneca vaccination Introduced in March 2021, Our understanding of a coagulopathy called thrombosis with vaccine-induced thrombocytopenia (VITT) or thrombocytopenia syndrome (TTS) has deepened.

We now know how to diagnose and treat it, so better results may be seen for patients with that condition.

How common and deadly is it?

Thankfully, development Blood clot Very rare after the AstraZeneca vaccine.

To date, Australia has 24 TTS out of 2.1 million AstraZeneca vaccines. Reported.. Therefore, the risk of TTS is about 1 in 88,000.

these The numbers are similar To those reported in the United Kingdom, Europe, the Middle East and Canada.

But Early reports from Europe In Australia, it has been shown that about 20% of TTS cases have been fatal so far, and one of 24 TTS cases is fatal, just over 4%.

What exactly is thrombosis with thrombocytopenia?

Although not yet fully explained, the AstraZeneca vaccine seems to be able to activate platelets. Platelets are small cells in the blood that are important for forming blood clots that prevent bleeding.

In some people, activated platelets can release a protein called Platelet Factor 4 (PF4) that binds to the AstraZeneca vaccine. This PF4 binding is Immune system It activates more platelets and causes them to stick together, thereby reducing their number. This leads to blood clotting (thrombosis) and a decrease in platelet count (thrombocytopenia).

Having a blood clot with a low platelet count is an important feature of TTS.

Different from other blood clots

This mechanism is quite different from the normal process by which blood clots develop.

Because TTS appears to be due to an irregular immune response, Current evidence Heart attack, stroke, Deep vein thrombosis, Pulmonary embolism (pulmonary thrombosis) or conventional anticoagulants do not increase the risk of TTS.

However, as a precautionary measure, the Pfizer vaccine is currently available. Recommended for those under 50, Or A person with history Decreased blood clots in the brain, abdomen, or previous platelet count reduction after taking the anticoagulant heparin.

Improved testing and treatment

A key development is diagnostic tests and guidelines for recognizing and treating cases of TTS.In most cases the patient platelet Count, blood evidence Blood clot, And antibodies against PF4. Many of these tests can be performed quickly.

Treatment can be started immediately with certain anticoagulants and drugs that weaken the immune system.

As of the latest May 20 Vaccine safety report After being released, 21 of the 24 Australians with TTS recovered and were discharged, and two were stable and recovered in the hospital.

So what side effects are normal and what indicates a blood clot?

Common side effects are common after vaccination. For AstraZeneca vaccines, these occur in the first two days after vaccination and include:

• headache
• Fever (chills)
• Muscle and joint pain
• nausea
• Malaise
• Pain at the injection site. It tends to be solved by simple methods such as paracetamol.

TTS thrombosis often occurs in abnormal locations such as the abdominal veins (visceral vein thrombosis) and the brain (cerebral vein sinus thrombosis). They usually occur 4 to 30 days after vaccination.

Therefore, symptoms that may indicate TTS after obtaining AstraZeneca vaccine include:

• Persistent or severe headache
• Blurred vision or diplopia
• Dyspnea
• Severe abdominal, back or chest pain
• Edema, redness, pain in the legs
• Abnormal bleeding or bruising.

If any of these symptoms occur 4 to 30 days after vaccination, see an urgent doctor.

Balance risk and benefit

TTS is very rare, but some people are concerned and want to talk to their doctor. This is essential to enable people to make informed choices.

However, due to the continued risk of COVID outbreaks in Australia and their potential fatal consequences, and the potentially serious long-term effects of COVID-19, for the majority of people, vaccination against COVID-19 The benefits soon outweigh the risks.

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