EU Regulator Finds "Very Rare" AstraZeneca Vaccine Blood Clot Risk: The Symptoms To Watch For

The AstraZeneca COVID-19 vaccine could lead to blood clots in a small subset of people, the European drug regulator has concluded, though it's a "very rare" possibility and shouldn't prevent immunizations in general. The European Medicines Agency (EMA) had been assessing the safety of Vaxzevria – developed by the University of Oxford in the UK and AstraZeneca – after reports of an uptick in dangerous blood clots among some people who had been given the drug.

It led to several countries halting use of the vaccine while further investigations were carried out. Earlier this week, the University of Oxford paused a trial among younger patients that had been exploring whether Vaxzevria could be used for under-18 year olds.

The EMA's safety committee, PRAC, has announced its investigation findings today, recommending that though a new warning should be added to the vaccine about its "very rare side effects," the overall benefit-risk remains positive.

"EMA is reminding healthcare professionals and people receiving the vaccine 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," the Agency said in a statement today. "So far, most of the cases reported have occurred in women under 60 years of age within 2 weeks of vaccination. Based on the currently available evidence, specific risk factors have not been confirmed."

Reviews of 62 cases of blood clots in the brain (cerebral venous sinus thrombosis, or CVST) and 24 cases in the abdomen (splanchnic vein thrombosis). Of those, 18 had proved fatal, from a total immunized population of around 25 million people in the European Union and the UK. The current theory is that an immune response is to blame for the blood clots and low blood platelets, with further investigation underway.

"COVID-19 is associated with a risk of hospitalisation and death," the EMA points out. "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. EMA's scientific assessment underpins the safe and effective use of COVID-19 vaccines."

Still, even if the side-effects are rare, they're things that people vaccinated with the AstraZeneca drug should be watching out for. The EMA recommends seeking medical assistance immediately should any of the following symptoms be noticed:

Shortness of breath

Chest pain

Swelling in your leg

Persistent abdominal (belly) pain

Neurological symptoms, including severe and persistent headaches or blurred vision

Tiny blood spots under the skin beyond the site of injection

Currently, Vaxzevria is not in use in the US. It is one of four vaccines that are authorized in the EU for protecting against COVID-19. "The chance of having this occur is very low," the EMA insists, "but you should still be aware of symptoms so you can get prompt medical treatment to help recovery and avoid complications."