COVID-19 vaccine, but insisted the benefits of the shot outweigh the risks.
The U.K. regulator — the Medicines and Healthcare products Regulatory Agency (MHRA) — also said the cases were “extremely rare” and stressed the benefits outweigh the risks for the “vast majority” of people, and recommended no age restrictions on the vaccine.
However, Dr. June Raine, chief executive of the MHRA, said that for young people it was more “finely balanced.” As a result, the U.K. government’s Joint Committee on Vaccination and Immunisation said people under the age of 30 would be offered an alternative vaccine, such as the one made by German biotech BioNTech
with U.S. drug company Pfizer
or the shot from U.S. biotech Moderna
The MHRA said the evidence of a link between the AstraZeneca vaccine and unusual blood clots is “stronger but more work is still needed,” while the European Medicines Agency (EMA) said it had found a “possible link.”
By March 31, 20.2 million doses of AstraZeneca’s vaccine had been administered in the U.K., meaning the overall risk of these blood clots is approximately four people in a million who receive the vaccine, the MHRA said.
The EMA set out its own conclusions on Wednesday following an in-depth investigation into the possible link between reported cases of rare blood clots and the U.K.-Swedish drug company’s vaccine.
The in-depth review looked into 62 cases of cerebral venous sinus thrombosis and 24 cases of splanchnic vein thrombosis, 18 of which were fatal. The cases came mainly from spontaneous reporting systems of the European Economic Area and the U.K., where around 25 million people had received the vaccine, the EMA said.
It added that most of the cases have occurred in women under 60 within two weeks of vaccination.
The EMA’s safety committee urged people who have received the vaccine to seek medical help if they develop symptoms of blood clots and low blood platelets. The symptoms include shortness of breath, chest pain, leg swelling, abdominal pain, persistent headaches and tiny blood spots under the skin. The U.K.’s MHRA listed the same symptoms and echoed the EMA’s advice.
The EMA said 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, or HIT).
On Tuesday, the University of Oxford said it had paused a small U.K. trial testing the vaccine in children and teenagers, while the MHRA investigated a possible link with rare blood clots in adults.
AstraZeneca said on March 14 that its own review of safety data of more than 17 million people vaccinated in the U.K. and EU had shown no evidence of an increased risk of blood clots.
Shares in AstraZeneca were trading 1% lower in afternoon trading in London and have now fallen 2.9% year-to-date.
The majority of EU countries restarted using the AstraZeneca vaccine late last month, after the EMA concluded that the shot is “safe and effective” and “not associated with an increase in the overall risk of blood clots.”
However, some countries, including France and Germany, have limited the use of the shot for people younger than 60.