Younger adults are most at risk of rare blood clotting after having the Oxford-AstraZeneca vaccine, the UK’s medicines regulator has said.

The Medicines and Healthcare products Regulatory Agency (MHRA) said there were 209 cases in the UK of the rare combination of blood clots with low platelet counts following being vaccinated the Oxford-AstraZeneca jab, with 41 deaths, up to April 21.

This is up from 168 cases and 32 deaths the previous week.

New data, published by the MHRA for the first time on Thursday, also gives a breakdown of the jab’s side affects by age.

It shows 23 cases in people aged 18 to 29, 27 in those in their thirties, 30 in people in their forties, 59 in people in their fifties and 57 in those aged 60 and above, with the age not known in the remaining cases.

Around a quarter of the rare blood clots were in people aged under 40, and two-thirds in those under 60, the data shows.

This is contrast to the proportion of people who have been vaccinated, with the latest NHS England data showing that 5.5 million people under 45 had received a first dose by April 25 compared to 22.6 million of those 45 and over.

The MHRA said that the data suggested there is a higher incidence reported in the younger adult age groups and advised that this evidence should be taken into account when considering the use of the vaccine.

Chief executive Dr June Raine said that no medicine or vaccine was without risk, but said the blood clots were “extremely rare”.

She added: “The benefits of the vaccine continue to outweigh the risks for most people.

“It is still vitally important that people come forward for their vaccination when invited to do so.

“We ask anyone who suspects they have experienced a side effect linked with their COVID-19 vaccine to report it to the Coronavirus Yellow Card website.”

The estimated number of first doses of Covid-19 Vaccine AstraZeneca administered in the UK by April 21 was 22 million giving an overall case incidence of 9.3 per million doses, The MHRA said.

The data also showed that 120 cases were recorded in women and 89 men aged from 18 to 93 years, and the overall case fatality rate was 19%.

The UK drugs regulator has already recommended people aged 30 and below are offered an alternative vaccine to the AstraZeneca jab due to some concerns over rare blood clotting.