A third coronavirus vaccine is being rolled out in the UK, as investigations continue into a potential association between the Oxford/AstraZeneca jab and a rare form of blood clot.

People in Wales will receive the first doses of the Moderna vaccine today.

The UK has bought 17 million doses of that vaccine – enough for 8.5 million people.

Jabs will be given out at West Wales General Hospital in Carmarthen in what has been hailed as “another key milestone” in the fight against coronavirus.

It comes as a trial of the Oxford/AstraZeneca vaccine in children has been 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”, as 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.