“There is now some evidence that the reported incidence rate is higher in females compared to men although this is not seen across all age groups and the difference remains small,” the Medicines and Healthcare products Regulatory Agency (MHRA) said on Thursday.

UK health officials previously said that the rare cases of unusual blood clots – or thromboembolic events – among vaccine recipients were associated with younger people and that they hadn’t seen a link to gender.

Earlier this year a number of European countries reported cases of blood clots in people who had received AstraZeneca’s Vaxzevria jab, prompting a review by the EU’s drug regulator, the European Medicines Agency (EMA).

The EMA’s findings, published last month, said that blood clots should be listed as “very rare side effects” of the vaccine and that most cases of blood clots occurred in women under 60 within two weeks of vaccination.

In response to the EMA review, several countries slapped age restrictions on the Anglo-Swedish jab, including the UK, which recommended that people under 30 should be offered an alternative vaccine.

The MHRA said that by April 28 around 22.6 million people in the UK had received a first dose of AstraZeneca's vaccine.

Among this group, it said there were 141 reports of blood clots in women and 100 cases in men, with a total of 49 cases proving fatal.

“The advice remains that the benefits of the vaccine outweigh the risks in the majority of people,” the MHRA said.