EMA finds possible link to AstraZeneca vaccine and very rare cases of unusual blood clots: Regulator not recommending age or gender restrictions

By Jane Byrne

- Last updated on GMT

© GettyImages/cagkansayin
© GettyImages/cagkansayin

Related tags Ema Astrazeneca

The European Medicines Agency’s safety committee, PRAC, has concluded there is a possible link between the use of AstraZeneca’s COVID-19 vaccine and rare side effects of unusual blood clots and low blood platelets in individuals who received the shot.

After an in-depth analysis, the committee confirmed today (April 7) that the reported cases of unusual blood clots following vaccination with AstraZeneca COVID-19 vaccine should be listed as possible side effects of the jab.

Sabine Straus, PRAC chair, in a press briefing, said: “No specific risk factors could be identified, based on the current data. The PRAC is not recommending any specific measures to reduce the risk."

Although most of the cases occurred in people under 60 years and in women, within two weeks of vaccination, she said that, due to different ways the vaccine in being use in different countries, the PRAC did not conclude that age and gender were clear risk factors for these very rare side effects.

The EMA said the overall benefit-risk from using the vaccine remains positive. “COVID-19 is associated with a risk of hospitalization 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."

PRAC, in reaching its conclusion, said it took into consideration all currently available evidence, including the advice from an ad hoc expert group. 

Emer Cooke, EMA's executive director, said the agency will continue to monitor all the scientific evidence available on both effectiveness and safety of all the authorized COVID-19 vaccines and will issue further recommendations, if necessary, on the grounds of robust evidence.

“It is important that both vaccinated people and healthcare professionals are aware of the signs and symptoms of these unusual blood clotting disorders and can spot them quickly to minimize the risk," ​she said. 

The EMA is working with the national competent authorities of the EU Member States and AstraZeneca to make sure that these risks are proactively communicated to healthcare professionals, said Cooke. 


PRAC noted that 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.

The committee said it carried out an in-depth review of 62 cases of CVST and 24 cases of splanchnic vein thrombosis reported in the EU drug safety database, EudraVigilance, as of March 22, 2021, 18 of which were fatal.

The cases came mainly from spontaneous reporting systems of the EEA and the UK, where around 25 million people had received the vaccine.

One plausible explanation for the combination of blood clots and low blood platelets is an immune response, leading to a condition similar to one seen sometimes in patients treated with heparin - heparin induced thrombocytopenia, HIT, said the committee.

UK watchdog’s review concurs with EMA’s findings

The UK regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), has also been reviewing the issue.

A statement​ it released today echoed the findings of the EMA, with the MHRA concluding that there is a possible link between COVID-19 Vaccine AstraZeneca and extremely rare, unlikely to occur blood clots.

However, like the EMA, the UK watchdog is not recommending age restrictions in the use of AstraZeneca's vaccine. It stressed the benefits of the shot in preventing COVID-19 far outweigh the risks but advised that careful consideration be given to people who are at higher risk of specific types of blood clots because of their medical condition.

Alternative vaccine advised for UK adults under 30, EU countries split on approach 

However, the Joint Committee on Vaccination and Immunization (JCVI) in the UK is advising that for adults aged under 30, if these persons are still unvaccinated, it is preferable for them to be offered an alternative COVID-19 vaccine, if available.   

And, soon after the EMA statement, Italy and Spain stopped the use of AstraZeneca COVID-19 vaccine in the under-60s. Belgium is restricting the shot to those aged 56 and above,​ France advises that it should be given only to those aged 55 or over, and in Germany it is recommended for those over 60.

Andrew Pollard, professor of pediatric infection and immunity, and chief investigator on the Oxford-AstraZeneca vaccine trial, commented on the events:

'Safety has been our priority throughout the development of the vaccine at Oxford University in 2020, and we are reassured to see that safety monitoring continues under the close scrutiny of regulators and public health authorities as the vaccine is rolled out around the world.

'The identification of rare cases of blood clots, which might be associated with the vaccine, shows that the safety system works, and has also allowed MHRA and EMA to conclude that the benefits of vaccination continue to outweigh the risks, while putting in measures to help mitigate any possible risk.

'The pandemic coronavirus continues to be a huge threat to people throughout the world, and we continue with our mission to support global vaccination, not for profit, for the benefit of humanity.'

This article was updated on April 8 to take account of developments following the EMA and MHRA statements. 

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