The Times Australia
The Times World News

.
The Times Real Estate

.

A history of blood clots is not usually any reason to avoid the AstraZeneca vaccine

  • Written by Sant-Rayn Pasricha, Division Head, Population Health and Immunity, Walter and Eliza Hall Institute

As haematologists, we look after many patients who have had blood clots in the past or take blood thinners. They often ask: “should I have the AstraZeneca vaccine?”

The answer is usually a definitive “yes”. The blood clots we’ve seen following the AstraZeneca vaccine are completely different to other types of blood clots, such as deep vein thrombosis or a pulmonary embolism, or the clots that cause heart attacks and strokes.

People with a history of these sorts of conditions don’t appear to be at any increased risk[1] from the AstraZeneca vaccine.

In fact, people in this group could be at greater risk[2] from COVID-19, so shouldn’t delay getting vaccinated.

First, how does blood form clots?

Blood flows through our body’s vessels as a liquid, carrying oxygen, nutrients, proteins and immune cells to every organ. But if we get injured or undergo surgery, our body needs to plug the wound to stem bleeding.

Our blood contains components that allow it to quickly transform from a fluid into a semi-solid clot[3] in a few seconds.

At the first sign of damage, the smallest of the blood cells — the platelets — stick to the damaged vessel wall, and together with the damaged wall itself, attract a legion of clotting proteins, which amass on the damaged site and bind the wound.

Read more: How rare are blood clots after the AstraZeneca vaccine? What should you look out for? And how are they treated?[4]

Venous clots

Sometimes theses natural clotting and anti-clotting processes in the blood become unbalanced, putting a person at risk[5] of developing blood clots in their veins. This can occur in people:

  • with cancer or an infection

  • who are pregnant

  • who are taking an oestrogen-containing contraceptive pill

  • who are immobilised during and after surgery or following major trauma

  • who have certain inherited conditions.

In all of these cases, an abnormal blood clot can develop in the deep veins of the thigh and groin (deep vein thrombosis), or the lung (pulmonary embolism).

Very rarely, blood clots occur in other places — for example, the veins of the abdomen or the brain.

An illustration of a blood clot. Our blood needs to clot to a degree. Shutterstock[6]

Arterial clots

Arteries supplying blood to the heart, brain and lower limbs can become narrowed[7], usually due to risk factors including smoking, diabetes, and high blood pressure and cholesterol.

A clot forming in these sites can obstruct blood flow, causing, for example, a heart attack or stroke.

What is TTS?

The AstraZeneca vaccine is associated with a rare condition called thrombosis with thrombocytopenia syndrome, or TTS[8]. Cases of the condition have also been reported following the Johnson & Johnson COVID vaccine[9], though this one isn’t available in Australia.

We now know a lot more about this condition than we did a few months ago.

TTS is caused by an abnormal immune response[10], resulting in the development of an antibody directed at the platelets[11] (blood cells which prevent bleeding). This causes the platelets to become hyperactive, which triggers blood clots in the body, including in places we don’t normally see clots, like in the brain or the abdomen.

This process also consumes platelets, which results in a low platelet count. In the name “thrombosis” refers to clots, and “thrombocytopenia” to low platelet count.

Read more: What is thrombocytopenia, the rare blood condition possibly linked to the AstraZeneca vaccine?[12]

The Australian Technical Advisory Group on Immunisation (ATAGI) recently estimated the risk of TTS in Australia at around 1.6 in 100,000[13] doses of the AstraZeneca vaccine administered in people 50 and older, although this data may change as more people are vaccinated.

Fortunately, diagnosis and treatment[14] for TTS has progressed rapidly. Doctors now know the symptoms to look out for, and haematologists have identified treatments for the condition[15]. These include intravenous immunoglobulin (a concentrate of antibodies from healthy donors) and blood thinners.

Outcomes for people with TTS have improved significantly worldwide since the condition was first recognised earlier in the year. In Australia, most patients[16] with TTS have recovered or are recovering.

A man prepares a syringe with the AstraZeneca vaccine. We’re now better at recognising and treating TTS. James Ross/AAP

Don’t delay getting the vaccine

There’s no evidence[17] people who have previously experienced blood clots, have an inherited risk of blood clots, or who take blood thinners or related medications, have any increased risk[18] of TTS.

As an immune-driven disease that causes platelet over-activity, the mechanism for TTS is completely different from other types of blood clots.

In this light, ATAGI recently advised the AstraZeneca vaccine is safe for these people.

As a precaution, Australian guidelines[19] recommend certain people should avoid the AstraZeneca vaccine and have the Pfizer jab instead. These include people:

Read more: People with coronavirus are at risk of blood clots and strokes. Here's what we know so far[20]

It’s crucial to remember that people with risk factors for heart attacks and strokes, including diabetes[21] and high blood pressure, are at increased risk of developing severe COVID-19[22] if they are infected. Further, COVID itself[23] makes the blood more “sticky” and significantly increases the risk of blood clots.

So we advise our patients: even if you’ve had deep vein thrombosis, a pulmonary embolism, a heart attack or a stroke previously, you’re not at increased risk of TTS from vaccination. You should get vaccinated as soon as you’re eligible.

References

  1. ^ increased risk (www.health.gov.au)
  2. ^ at greater risk (www.thelancet.com)
  3. ^ clot (www.ncbi.nlm.nih.gov)
  4. ^ How rare are blood clots after the AstraZeneca vaccine? What should you look out for? And how are they treated? (theconversation.com)
  5. ^ at risk (bestpractice.bmj.com)
  6. ^ Shutterstock (www.shutterstock.com)
  7. ^ become narrowed (www.nhlbi.nih.gov)
  8. ^ or TTS (www.health.gov.au)
  9. ^ Johnson & Johnson COVID vaccine (post.parliament.uk)
  10. ^ immune response (www.nejm.org)
  11. ^ antibody directed at the platelets (www.nejm.org)
  12. ^ What is thrombocytopenia, the rare blood condition possibly linked to the AstraZeneca vaccine? (theconversation.com)
  13. ^ around 1.6 in 100,000 (www.health.gov.au)
  14. ^ diagnosis and treatment (www.thanz.org.au)
  15. ^ treatments for the condition (www.thanz.org.au)
  16. ^ most patients (www.tga.gov.au)
  17. ^ no evidence (www.nejm.org)
  18. ^ have any increased risk (www.health.gov.au)
  19. ^ guidelines (www.health.gov.au)
  20. ^ People with coronavirus are at risk of blood clots and strokes. Here's what we know so far (theconversation.com)
  21. ^ diabetes (www.thelancet.com)
  22. ^ severe COVID-19 (www.thelancet.com)
  23. ^ COVID itself (erj.ersjournals.com)

Read more https://theconversation.com/a-history-of-blood-clots-is-not-usually-any-reason-to-avoid-the-astrazeneca-vaccine-161889

The Times Features

Best Deals on Home Furniture Online

Key Highlights Discover the best deals on high-quality outdoor furniture online. Transform your outdoor space into a stylish and comfortable oasis. Explore a wide range of d...

Discover the Best Women's Jumpers for Every Season

Key Highlights Explore lightweight jumpers for spring and summer, ensuring breathability and ease. Wrap up warm with cozy wool jumpers for the chilly autumn and winter season...

Uncover the Elegance of Gorgeous Diamond Tennis Necklaces

Key Highlights Diamond tennis necklaces are a timeless piece of jewelry that exudes elegance and sophistication. They feature a continuous line of brilliant-cut diamonds, cre...

Dental Implants vs. Dentures: Which Is Better for You?

When it comes to replacing missing teeth, two of the most common options are dental implants and dentures. Both have their advantages and disadvantages, so choosing between them ...

What Neck Pain Really Means (And Why It’s More Than Just Poor Posture)

Neck pain is often brushed off as something temporary — a tight spot after a long day at the desk or a poor night’s sleep. But when the discomfort keeps returning, it could be a ...

The Work of Gosha Rubchinskiy: Fashion, Culture, and Youth

From Designer to Cultural Architect Gosha Rubchinskiy is not just a fashion designer—he's a cultural force. Born in Moscow in 1984, Rubchinskiy began his career in fashion in t...

Times Magazine

The Essential Guide to Transforming Office Spaces for Maximum Efficiency

Why Office Fitouts MatterA well-designed office can make all the difference in productivity, employee satisfaction, and client impressions. Businesses of all sizes are investing in updated office spaces to create environments that foster collaborat...

The A/B Testing Revolution: How AI Optimized Landing Pages Without Human Input

A/B testing was always integral to the web-based marketing world. Was there a button that converted better? Marketing could pit one against the other and see which option worked better. This was always through human observation, and over time, as d...

Using Countdown Timers in Email: Do They Really Increase Conversions?

In a world that's always on, where marketers are attempting to entice a subscriber and get them to convert on the same screen with one email, the power of urgency is sometimes the essential element needed. One of the most popular ways to create urg...

Types of Software Consultants

In today's technology-driven world, businesses often seek the expertise of software consultants to navigate complex software needs. There are several types of software consultants, including solution architects, project managers, and user experienc...

CWU Assistive Tech Hub is Changing Lives: Win a Free Rollator Walker This Easter!

🌟 Mobility. Independence. Community. All in One. This Easter, the CWU Assistive Tech Hub is pleased to support the Banyule community by giving away a rollator walker. The giveaway will take place during the Macleod Village Easter Egg Hunt & Ma...

"Eternal Nurture" by Cara Barilla: A Timeless Collection of Wisdom and Healing

Renowned Sydney-born author and educator Cara Barilla has released her latest book, Eternal Nurture, a profound collection of inspirational quotes designed to support mindfulness, emotional healing, and personal growth. With a deep commitment to ...

LayBy Shopping