The Moderna vaccine has become the third to be rolled out in the UK in what has been dubbed “another key milestone” in the fight against coronavirus.
People in Wales will start receiving the jab from Wednesday and it will reportedly be in England in “the next few days”.
The UK has bought 17 million doses – enough for 8.5 million people.
But the good news comes as as a trial of the Oxford/AstraZeneca vaccine in children was paused while regulators investigate reports of a rare form of blood clot among adults.
The University of Oxford said no safety concerns have arisen from the children’s trial and Sage adviser Professor Calum Semple said the decision to pause had been made out of “exceptional caution”. He urged people to continue accepting Oxford/AstraZeneca jabs.
Assessments are under way into a very rare and specific type of blood clot in the brain, known as cerebral venous sinus thrombosis (CVST), occurring together with low levels of platelets (thrombocytopenia) following vaccination in adults.
The World Health Organisation (WHO) and the European Medicines Agency (EMA) are expected to announce findings of their assessments on Wednesday or Thursday.
The UK’s regulator – the Medicines and Healthcare products Regulatory Agency (MHRA) – is also investigating reports but has not confirmed when it will present its findings.
Both the MHRA – which said it had identified 30 cases of rare blood clot events out of 18.1 million doses of the jab administered up to and including March 24 – and WHO have said that to date the benefits of the vaccine in preventing coronavirus outweigh any risks.
Health secretary Matt Hancock said he was “delighted we can start the UK rollout of the Moderna vaccine in west Wales today”.
He added: “The UK government has secured vaccines on behalf of the entire nation and the vaccination programme has shown our country working together at its best.”
Wales health minister Vaughan Gething said: “This is another key milestone in our fight against the Covid-19 pandemic.”
The rollout will start in England “as soon as possible this month”, a spokesperson for the Department of Health and Social Care said, but added that commercial sensitivities prevented further disclosures.
Vaccines minister Nadhim Zahawi said on Tuesday that the Moderna jab would be deployed “around the third week of April”.
Scotland’s first minister Nicola Sturgeon said the first batch of Moderna vaccines had arrived in the country on Monday and will be delivered over the coming months.
It has not been confirmed when the rollout of Moderna will begin in Northern Ireland.
More than 31m first doses of either the Pfizer or AstraZeneca vaccines have been administered in the UK, according to government data up to April 5, while more than five million second doses have been given out.