AstraZeneca vaccine: Blood clots should be listed as 'very rare' side effect, says EU regulator

The benefits of the COVID-19 vaccine still outweigh the risks of possible side effects, says the European Medicines Agency.

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Europe's AstraZeneca vaccine is possibly linked to blood clots.

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A possible link between AstraZeneca's COVID-19 vaccine and very rare cases of unusual blood clots has been found, the European Union's drug regulator said Wednesday. However, it added the overall benefits of the shot outweigh the risk of side effects.

The European Medicines Agency concluded that "unusual blood clots with low blood platelets should be listed as very rare side effects" of AstraZeneca's COVID-19 vaccine, the regulator said in a release. The assessment comes after an expert committee reviewed reports of unusual blood clots in people who had received the vaccine.

Watch this: COVID-19 vaccines and blood clots explained

Most of the cases occurred in women under 60, said the EMA, but there's not yet enough evidence to confirm specific risk factors. The regulator said it's important for health care professionals and vaccinated people to be aware of the signs of these rare blood clots, including shortness of breath, chest pain, leg swelling and persistent abdominal pain as well as neurological symptoms, such as severe and persistent headaches or blurred vision. 

AstraZeneca's vaccine came under scrutiny after the deaths of two vaccinated patients in March prompted some European countries to pause their rollout while the EMA investigated. On Wednesday, EMA Executive Director Emer Cooke reiterated that the benefits of the vaccine outweigh the risks of side effects.

"The risk of mortality from COVID is much greater than the risk of mortality from these side effects," said Cooke during a briefing. "I think it's important that we give the message that vaccines will help us in the fight against COVID and we need to continue to use these vaccines."

AstraZeneca didn't immediately respond to a request for comment.