The European Medicines Agency reiterated that the AstraZeneca vaccine had been “proven to be highly effective” and that vaccination as a whole is “extremely important” in the fight against Covid-19.

Blood clots will be listed as possible side effects of the jab following a small number of reported cases.

But overall, the EMA' executive director Emer Cooke stressed that the protection the vaccine offers against the deadly disease of coronavirus makes it worth taking.

She told a Brussels press briefing: “First of all, I want to start by stating that our safety committee, the Pharmacovigilance and Risk Assessment Committee (PRAC) of the European Medicines Agency, has confirmed that the benefits of the AstraZeneca vaccine in preventing Covid-19 overall outweigh the risks of side effects.

“Covid-19 is a very serious disease with high hospitalisation and death rates and everyday Covid is still causing thousands of deaths across the EU.

“This vaccine has proven to be highly effective – it prevents severe disease and hospitalisation, and it is saving lives.

“Vaccination is extremely important in helping us in the fight against Covid-19 and we need to use the vaccines we have to protect us from the devastating effects.

“The PRAC, after a very in-depth analysis, has 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.”

The benefits of the AstraZeneca vaccine outweigh the risks for the “vast majority” of people after cases of blood clots were detected in an “extremely small” number of people, Dr June Raine, chief executive of the Medicines and Healthcare products Regulatory Agency said.

She added: “The evidence is firming up and our review has concluded that while it’s a strong possibility, more work is needed to establish beyond all doubt that the vaccine has caused these side effects.

“Our review has reinforced that the risk of this rare suspected side effect remains extremely small.”