Coronavirus

What We Know About The AstraZeneca Blood Clots

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The human body needs a continuous flow of blood through it to keep us alive.   

If we get an injury, like a cut, blood clots help that injury to heal. They act kind of like a plug to stop blood leaking out.   

The body usually breaks down the clot once that injury has healed. But sometimes that doesn’t happen, and those blood clots can form inside arteries or veins.   

Kind of like what happened with the ship that got stuck in the Suez Canal.   

If that happens it can be really dangerous and even fatal, which is why when reports of fatal blood clots appearing in people who had had the AstraZeneca Covid vaccine started appearing, the alarm got rung.

In early 2021, millions of people across the world had received, or were getting ready to receive, one of the approved vaccines against Covid-19.   

The vaccines were a turning point in the global pandemic, which to date has killed over 3.1 million people around the world.   

But by the end of March, 19 people in the UK who had all had the AstraZeneca vaccine had died. All 19 people had suffered a type of blood clot.   

A medical agency in Europe reviewed the cases and wrote that they thought there was a possible link between the AstraZeneca vaccine and “extremely rare, unlikely to occur blood clots”.   

And the weird thing was, no one had ever really seen these kind of blood clots caused by a vaccine before.   

Dr. Paul Griffin, Director of Infectious Diseases, Mater Hospital: “You know, something like this has not really been seen before in vaccines.”  

18 other cases where blood clots had been fatal had already been identified throughout Europe.   

But The World Health Organisation was adamant that the evidence at the time wasn’t enough to say outright that there was a link between the clots and the AstraZeneca vaccine.   

They wanted governments to keep their focus on rolling out vaccines; to remember how many deaths Covid-19 had caused, and to focus on reducing that number through vaccinating their populations.    

But various European countries, like Germany, France, Spain, and Italy, had already started suspending their AstraZeneca rollouts, because of the potential link between blood clots.   

By the end of March, Australia was in the second phase of its vaccine rollout, phase 1B. Some people were being given the Pfizer vaccine, and others the AstraZeneca.   

Scott Morrison had even announced that Australia had secured nearly 54 million doses of the AstraZeneca vaccine.   

But the number of google searches for ‘blood clots’ in Australia had jumped dramatically, and in early April the Therapeutic Goods Administration announced that they were investigating a probable case of the clotting disorder here, in a man who had received the AstraZeneca vaccine.   

Researchers are still just trying to understand these blood clots seen in AstraZeneca patients more. They’re provisionally being called vaccine induced prothrombotic immune thrombocytopenia (VIPIT).   

It’s only a provisional name because this is the first time researchers have ever seen something like this following a vaccine.   

From the cases that have been studied so far, it’s the induced thrombocytopenia that seems to be causing people to die; a condition that causes low blood platelet levels and increases risk of excessive bleeding.   

In most of the deaths that have occurred, patients had incidents of blood leaks and clotting in the brain.   

What researchers are still trying to figure out though, is why the AstraZeneca vaccine might be causing this particular condition, and why it’s happening in younger people.   

It’s a hard task considering this is a new vaccine, and that blood clots weren’t picked up during the clinical trials of AstraZeneca.   

Associate Professor Matthew Linden, University of Western Australia: We learn more with every new case, but thankfully every new case is so rare that we’re not learning a lot. 

By the time the UK recorded those 19 deaths at the end of March, around 20 million British people had had the AstraZeneca vaccine.    

According to the TGA, the three cases Australia has seen equates to roughly a 1 in 295,000 chance of developing blood clots after having the AstraZeneca vaccine.   

And in an address that was aimed at downplaying the severity of the AstraZeneca blood clots, Scott Morrison tried to point out that clots have always existed.  

Even sitting still on a long-haul flight for too long can cause a blood clot, and one woman in her early 20s with polycystic ovary syndrome told me that she experiences multiple blood clots between and leading up to her periods.   

But for the nearly 80% of Australians who use the pill at some stage of their life, even with the risks involved, ScoMo’s comment really backfired. 

Experts have since pointed out that someone’s risk of dying from a blood clot as a result of the pill is around 3%. Whereas for people who develop blood clots after getting the AstraZeneca vaccine, the risk of dying is around 25%.   

So where do we stand now? From global data, the likelihood of developing a blood clot after receiving the AstraZeneca vaccine is estimated to be around four to six cases per 1 million recipients.    

Overall, the chances of developing blood clots are believed to be pretty slim.   

But because there is that 25% chance of death in the incident of a clot, health experts around the world are taking the chances really seriously.   

Germany has now resumed its use of AstraZeneca after initially suspending it, and so have countries like France, Italy, and Spain. But most countries have now put in place new regulations on the AstraZeneca vaccine, limiting it from being given to young people.   

And earlier this month, after pausing the AstraZeneca vaccine here too, Australian health authorities advised that the Pfizer vaccine would be the more suitable vaccine for people under 50 to have moving ahead.   

That age bracket is for two main reasons. Firstly, the deadly blood clot cases are being found mostly in people under the age of 50.   

But secondly, because older people are more at risk of severe complications if they do contract Covid, then vaccinating and protecting them should be more of a priority.   

Of the 909 Covid deaths reported in Australia as of 8 April 2021, only 5 were in people under 50. In other words, 99.5% of Australian Covid-19 deaths were in those 50 and older.   

Dr. Paul Griffin: For this vaccine in people over 50 – where the risk of this really rare adverse event is much lower, and the risk of them getting really sick from Covid is higher – the benefits far outweigh the risks. So that’s why we’re really confident to use it in people over 50, but reluctant to do some people less than 50. 

The whole blood clot link to the AstraZeneca vaccine has caused huge alarm among the public, which in Australia has only been exacerbated by the delay to the government’s vaccine rollout plan.      

Australia has now secured 40 million Pfizer doses, but no one really knows just how much Pfizer is available right now.   

It’s also been pretty scary for the people under 50 who already had their first dose of AstraZeneca before the guidelines changed.   

For now, the advice is that if someone has had their first dose of AstraZeneca without any serious adverse effects, then they can be given their second dose too.   

But because these cases of blood clots are so rare, and because the research into them is still ongoing, and because no one knows what could happen with the pandemic itself, this could all completely change again.   

Dr. Paul Griffin: “Risks and benefits are very different for different people. At the moment, this assessment of benefits versus risks is based on us having such excellent control of Covid [in Australia]. That really could change the drop of a hat.”