Experts explain what is known between Astrazeneca vaccine’s link and thrombosis

Science does not yet know “what causes this reaction”. But an official from the European Medicines Agency (EMA) confirmed the link between the vaccine against coronavirus AstraZeneca and thrombosis.

“Now we can say it is clear that there is a link with the vaccineMarco Cavaleri, head of vaccine strategy at EMA, told Italian media The messenger.

The declaration has had an impact around the world, not only in the UK – the headquarters for the development of the technology of this formula -, and in particular in Argentina, where it is not only applied but partially manufactured and he is also received by Covax. The Covishield vaccine, which has also arrived in the country, is also the same AstraZeneca vaccine but made in India.

In Cavaleri’s words, it’s not yet clear why this is happening. “We are trying to get a clear picture of what is happening, to define precisely this syndrome due to the vaccine (…) Among those vaccinated, there is a greater number of cases of cerebral thrombosis in young people.”

For several weeks, this suspicion of possible serious side effects has been hovering over, following the observation in people vaccinated with AstraZeneca of cases of atypical thrombosis. In the UK, there have been 30 cases and seven deaths out of a total of 18.1 million doses administered as of March 24.

But, so far, the EMA has argued that “no causal link with the vaccine has been proven”, although it is “possible”, and that the benefits of vaccination against the coronavirus always outweigh the risks.

For Paul Hunter, a specialist in medical microbiology at the University of East Anglia, interviewed by AFP, “the evidence rather points to the fact that the Oxford-AstraZeneca vaccine is in fact the cause”.

As a precaution, several countries they have suspended their vaccination in certain age groups, such as those under the age of 60. These are France, Germany and Canada. Norway and Denmark have suspended its full use, “temporarily”.

For its part, AstraZeneca assured that “there is no evidence of an aggravation of the risk”, and last Saturday she assured that “patient safety” is her “main priority”.

Today, the link does not “cancel” the vaccine

The Pharmacovigilance Risk Assessment Committee (PRAC), which monitors and assesses the safety of medicinal products for human use authorized by the EMA, meets from Tuesday to Friday only to assess cases of thrombosis in those who have received this vaccine.

Everything would indicate that this week – we are even talking about this Wednesday – the report of its updated assessment on the security of AstraZeneca would be published.

At their last meeting last Wednesday, the PRAC did not rule out a cause and effect relationship, but also did not find clear evidence of a link between AstraZeneca and the development of blood clots with a low count. platelet.

Thus, the EMA continued to consider that the benefits of this vaccine against the coronavirus, a disease which kills nearly 60,000 in Argentina, they continue to overcome any risk by side effect.

“I think that in Argentina, the benefit will be prioritized over the risk. Because this direct link between these thromboses and the vaccine has not been proven,” he said. Bugle Pablo Pratesi, head of intensive therapy at Austral Hospital.

Pratesi explained that “coagulation is a clash of forces, between what the body needs to clot, for example, if you cut a finger, and what it should not clot, so as not to die of thrombosis. There has to be that balance. “

Finally, the expert added: “From what I have read about the cases, there is no direct cause between the formation of these atypical clots and the administration of doses of Astrazeneca.”

The first thing to understand, explains Rosa Reina, president of the Argentine Society of Intensive Care (SATI), is that disseminated intravascular coagulation, “is one thing and the syndrome Astrazeneca is supposed to produce, is another“.

The first is ‘multifactorial’ – it can occur after trauma in a car accident to infection or a contraindicated drug for the person – and is delivered by ‘thrombi’ in the body produced by a cascade of mediators. that activate coagulation.

“What is being studied about this vaccine is that an antibody would be generated, very rare, which would occur against one of the factors that promote coagulation: the anti-PF4, ”explains Reina.

This syndrome is very similar to that which occurs in reaction – “rare, very rare”, insists the doctor – in those who receive heparin, to prevent the formation of clots. “But it’s given one in a million or a million and a half patients. It’s very rare. And the same process is being studied in those who received the vaccine and developed this atypical thrombosis. When neither of those people was on heparin. But it remains to be investigated. Likewise, we speak of 30 cases every two million vaccinated“, Stop.

“The crucial question remains whether these are post-vaccination or pre-vaccination defections … We must err on the side. It is prudent to press the pause button as a precaution, ”said Dutch Minister of Health Hugo de Jonge, stressing that“ the safety of vaccines cannot be in doubt ”.

Strange clots

Researchers have so far not identified any risk factors such as age, gender or a medical history of blood clotting disorders, which could explain these rare cases – the words they use are ” strange clots “- thromboembolism occurring after vaccination.

“People who have been vaccinated should be aware of the remote possibility these very rare types of blood clots occur. If they have symptoms suggesting coagulation problems as described in the product information, they should seek immediate medical attention and inform healthcare professionals of their recent vaccination, ”the EMA stressed.

This agency is analyzing all the suspected cases of unusual blood clots reported in recent weeks by the national authorities in each European country.

Early March, Austria was the first to recall a specific batch of AstraZeneca after a person was diagnosed with multiple thrombosis and died ten days later, having previously received an injection of this vaccine.

PS