People under the age of 40 in Britain will be offered an alternative to the Oxford/AstraZeneca COVID-19 vaccine following concerns of rare blood clots, The Daily Telegraph and The Independent newspapers report.
The Joint Committee on Vaccination and Immunisation (JCVI) has recommended that people instead be offered a Pfizer or Moderna vaccine out of "an abundance of caution", The Telegraph said.
A spokeswoman from Britain's Health Department said on Thursday the position of the JCVI and medicines regulator MHRA "continues to be that the benefits of the Oxford/AstraZeneca vaccine outweigh the risks for the vast majority of adults".
"The JCVI keep their recommendations under review in line with the latest scientific advice", the spokeswoman said in a statement, adding Britain was on track to offer a vaccine to all adults by the end of July.
In April, the JCVI advised alternatives to AstraZeneca's vaccine for those under 30. Pregnant women in the UK were told to have the Pfizer or Moderna vaccine.
In the latest weekly figures, Britain's medicine regulator said the case incidence of the rare clots and low platelet levels was 10.5 per million doses, compared with 9.3 per million last week.
The JCVI drafted recommendations earlier this week and an announcement from the government is expected on Friday, The Independent said.
The regulator on Thursday said there was some evidence that uncommon blood clots linked to AstraZeneca's vaccine occurred more in women than in men, adding the difference in incidence was small.
UK officials have previously only said that the incidence of the clots was linked to age and that a link with gender had not been established, noting that more women had been vaccinated then men.
"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 said in its weekly updates on the clots.
Up to April 28 there had been 22.6 million first doses of the AstraZeneca vaccine given in the UK, with 5.9 million second doses.
Australian Associated Press