Last reviewed 11 May 2021

Most adults under the age of 40 will be given an alternative to the Oxford-AstraZeneca vaccine due to a link with rare blood clots.

The Medicines and Healthcare Products Regulatory Agency (MHRA) has linked the Oxford-AstraZeneca Covid-19 vaccine to distinctive but rare blood clots that also appear with low levels of platelets in the blood.

Everyone aged under 40 will now be offered either the Pfizer or Moderna vaccine following the change in advice. The Joint Committee on Vaccination and Immunisation (JCVI) said it was putting "a high priority on safety" and expects that the move would "serve to boost confidence" in the vaccination programme.

Low levels of Covid-19 cases and the availability of alternative vaccines have informed the decision. After 28.5 million doses of the vaccine have been administered, there were 242 clotting cases and 49 deaths; the risk is slightly higher in younger age groups.

The JCVI’s Professor Wei Shen Lim said immunisation was estimated to have already saved 10,000 lives in the UK and added: "As Covid-19 rates continue to come under control, we are advising that adults aged 18 to 39 years with no underlying health conditions are offered an alternative to the Oxford-AstraZeneca vaccine, if available, and if it does not cause delays in having the vaccine."

The risk of a clot is roughly one in 100,000 for people in their 40s but rises to one in 60,000 for people in their 30s. Two in a million people in their 40s died, rising to 4 per million people in their 30s. Meanwhile, the risks of developing severe Covid, if the virus is caught fall in younger age groups.

MHRA Chief Executive Dr June Raine said the benefits of getting vaccinated continued to outweigh the risks for the "vast majority of people". She added: "The balance of benefits and risks is very favourable for older people but is more finely balanced for younger people."

In Wales, people under 40 years old will also no longer receive first doses of the Oxford-AstraZeneca vaccine due to the MHRA advice. However, those in their 30s who have had a first dose of the vaccine have been advised by Wales Deputy Chief Medical Officer Dr Gill Richardson to also get their second.

She said there had been no "rare events" recorded after receiving second doses. More than 1.2 million people in Wales have had the Oxford-AstraZeneca jab, with at least one case of the blood clot detected since the rollout began in January.

Most adults in Scotland under the age of 40 will also be given an alternative to the Oxford-AstraZeneca vaccine.