European Medicines Agency: Link Between AstraZeneca COVID Vaccine & Rare Blood Clots – But ‘Benefits Far Outweigh Risks’
Emer Cooke, EMA Executive Director, at Wednesday, 7 April press conference.

Following a second meeting of the EMA’s safety committee in as many weeks, the European Medicines Agency said that there appears to be a link between receipt of the AstraZeneca vaccine and very rare cases of blood clots being seen in some people – mainly younger women – within two weeks of their jab.

The linkage, however rare, is another blow to the rollout of the vaccine which is currently the most affordable and the most widely available, the world over.

It could stimulate more hesitancy and confusion about the vaccine’s use not only in Europe but in the dozens of low- and middle-income countries that are right now almost exclusively reliant upon AstraZeneca vaccine supplies – being provided free-of-charge by the WHO co-sponsored COVAX initiative. In India, where the vaccine is being produced under license, the vaccine, produced under license by the Serum Institute, is the centerpiece of a major vaccination rollout that aims to blunt a new wave of COVID cases, which saw over 100,000 new cases reported in the past 24 hours.

“The blood clots occurred in veins in the brain (cerebral venous sinus thrombosis, CVST) and the abdomen (splanchnic vein thrombosis) and in arteries, together with low levels of blood platelets and sometimes bleeding,” noted the EMA’s Pharmacovigilance Risk Assessment Committee (PRAC) in a statement issued on Wednesday.

Speaking at a press briefing, EMA Executive Director Emer Cooke stressed that the benefits of vaccination still outweigh the risks: “Our safety committee … has confirmed that the benefits of the AstraZeneca vaccine …. outweigh the risk of side effects. This vaccine has proved to be highly effective. It is preventing hospitalizations and saving lives.” However at the same time, she noted that “after a very in-depth analysis, the PRAC after a very in depth analysis had concluded that the reported cases of unusual blood clotting following vaccination with the AstraZeneca vaccine should be listed as possible side effects of the vaccine.”

She said that as of now, no specific risk factors had been identified that make people vulnerable to the rare condition – although the EMA statement noted that most of the cases reported have occured in women under the age of 60.

EMA Committee Stops Short of Policy Recommendations On Groups Most At Risk

At the same time, the committee stopped short of issuing a recommendation that the AstraZeneca vaccines be withheld from younger groups, or from younger women – saying there was still insufficient evdience to establish “a definite cause for these complications” or to link the cases to specific risk factors – including age or gender.

“Because of the different ways that the vaccine is being used in different countries, the commiteee did not conclude that age and gender were very clear risk factors for these very rare side effects,” said Sabine Straus, chair of the EMA’s PRAC safety committee, at the press briefing.

The EMA findings were also echoed by the World Health Organization, which issued its own statement Wednesday on the findings of the WHO Global Advisory Committee on Vaccine Safety, concluding that: “Based on current information, a causal relationship between the vaccine and the occurrence of blood clots with low platelets is considered plausible but is not confirmed. Specialised studies are needed to fully understand the potential relationship between vaccination and possible risk factors.”  However, based on the evidence so far, the WHO committee, like the EMA, did not recommend curbing vaccine administration among younger people, or younger women, at this time.

However, in the United Kingdom, regulators said on Wednesday that they would issue a new recommendation for people under the age of 30 to receive other types of vaccines.  And other Europan countries, such as Germany, recently limited the AstraZeneca vaccine to people over the age of 60.

The committee statement, however, urged that  “healthcare professionals and people receiving the vaccine [need] to remain aware of the possibility of very rare cases of blood clots combined with low levels of blood platelets occurring within 2 weeks of vaccination… People who have received the vaccine should seek medical assistance immediately if they develop symptoms of this combination of blood clots and low blood platelets.”

WHO, meanwhile, warned vaccinated individuals and their healthcare professionals to be on the lookout for specific symptoms, stating that: individuals who experience any severe symptoms – such as shortness of breath, chest pain, leg swelling, persistent abdominal pain, neurological symptoms, such as severe and persistent headaches or blurred vision, tiny blood spots under the skin beyond the site of the injection – from around four to 20 days following vaccination, should seek urgent medical attention. Clinicians should be aware of relevant case definitions and clinical guidance for patients presenting thrombosis and thrombocytopaenia following COVID-19 vaccination.

The EMA statement also stressed that risks associated to COVID remain much higher than those attributable to the vaccine: “COVID-19 is associated with a risk of hospitalisation and death.The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects.”

The most recent data from a large scale trial conducted in the United States, Peru and Chile, suggested that the AstraZeneca vaccine, developed together with Oxford University, is 79% effective at reducing the risk of symptomatic Covid-19, rising to 80% among people over the age of 65 – and 100% effective against severe disease.

But the statement also tacitly acknowledged that member states will also decide their policies, based on the mix of vaccines available: “Use of the vaccine during vaccination campaigns at national level will also take into account the pandemic situation and vaccine availability in the individual Member State.”

Committee Conducted In-depth Review of 86 cases of Blood Clot Conditions

The Committee said that it carried out an in-depth review of 62 cases of cerebral venous sinus thrombosis and 24 cases of splanchnic vein thrombosis reported in the EU drug safety database (EudraVigilance) as of 22 March 2021, 18 of which were fatal.

As of 4 April 2021, a total of 169 cases of CVST and 53 cases of splanchnic vein thrombosis had been reported to EudraVigilance among the 34 million people had been vaccinated in the European region and the United Kingdom by that date. “The more recent data do not change the PRAC’s recommendations. The cases came mainly from spontaneous reporting systems of the EEA and the UK, where around 25 million people had received the vaccine,” the commtitee also noted.

As for the mechanism, the committee said that the current thinking is that the vaccine may trigger an immune response leading to the blod clotting condition, which is similar to a reaction some people have to the administration of the blood thinner, heparin, called heparin-induced-thrombocytopenia like disorder.

Healthcare professionals involved in giving the vaccine in the EU will receive a direct healthcare professional communication (DHPC). The DHPC will also be available.

See the complete EMA statement here and the WHO Global Advisory Committee on Vaccine Statement here.



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