The UK has begun the rollout of its third coronavirus vaccine, the Moderna jab, in Wales.
Unpaid carer Elle Taylor said she was “very excited and happy” to be the first in the UK to receive the jab.
In England, small business minister Paul Scully said the vaccine would be rolled out “in the next few days”.
Meanwhile, there will be a televised briefing at 15:00 BST on potential links between the Oxford-AstraZeneca jab and rare blood clots.
England’s deputy chief medical officer Jonathan Van-Tam will be joined by June Raine, chief executive of the Medicines and Healthcare products Regulatory Agency, Sir Munir Pirmohamed, chairman of the Commission on Human Medicines, and Wei Shen, chairman of the Joint Committee on Vaccination and Immunisation.
European regulators are due to report their findings at the same time, and the World Health Organization is also continuing to assess the data.
Miss Taylor, from Ammanford, received the first Moderna jab at the Glangwili Hospital in Carmarthen.
Speaking after receiving the vaccine, the 24-year-old, who works at a further education college, said: “I’m very excited and very happy.
“I’m an unpaid carer for my grandmother so it is very important to me that I get it, so I can care for her properly and safely.
“My grandmother has had her first dose and she is going for her second dose on Saturday.”
Miss Taylor said she only found out on Tuesday evening that she was to be the first in the UK to receive the jab by Moderna, an American company.
Beverley Gower, from Kidwelly, who also received the jab, said she “didn’t feel it”.
The 49-year-old, who is also an unpaid carer so gets priority for the vaccine like Miss Taylor, added: “This is a way forward, isn’t it? A way back to normality.”
John Sanders from Carmarthenshire was the fifth person to receive the jab.
He said: “It’s massively important. I’m a carer for my disabled son who’s now 22. He’s had brain cancer and various chemotherapies and he’s got immune problems as well so it’s obviously important for us.”
The UK is committed to buying 17 million doses of Moderna, the third of seven vaccines developed in the UK or around the world that it has put in orders for.
It has not been confirmed when the rest of the UK will start using the jab, but Scotland received its first batch on Monday .
Like the Pfizer-BioNTech and Oxford-AstraZeneca jabs which are already in use, the Moderna jab is given in two doses, several weeks apart.
Health Secretary Matt Hancock said he was delighted the UK rollout of the Moderna vaccine was starting.
“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,” he said.
Wales’ Health Minister Vaughan Gething said a third vaccine for use in Wales “significantly adds” to the nation’s defences against Covid-19.
Across the whole of the UK, more than 31.6 million people have now had a first dose of a Covid vaccine – while 5.4 million have been fully vaccinated.
In Wales, more than 1.49 million people have had a first dose, while more than 469,000 people have had both doses.
Mr Scully told Sky News the vaccination programme remained on track to cover all adults in England by the end of July.
On Tuesday, the trial of the Oxford vaccine on children stopped giving out jabs as a precaution.