Mass vaccination centres in the Cwm Taf health board area will temporarily close due to supply issues, local politicians have said.
Three centres are expected to be closed for about a fortnight, because of supply issues with the Pfizer-BioNTech vaccine.
It comes as other vaccinations centres are expected to reduce their hours.
First Minister Mark Drakeford said a drop in supply had been planned for and is “accommodated in our plans”.
“We know that we are going to get less vaccine over the next few weeks than we have over the past few weeks,” he told a Senedd committee.
He said the plans remain to complete vaccinations of the next five priority groups by the spring.
Officials are also expecting fewer doses from AstraZeneca, before deliveries return to recent levels from the beginning of March.
Health boards will determine how vaccines are delivered over the next two weeks, with mass vaccination centres changing their opening times to reflect the reduction in supply.
Wales became the first UK nation on Wednesday to have given first doses to 20% of the population, after a slow start.
It is on course to meet its mid-February target of offering a jab to the over 70s and the clinically extremely vulnerable.
Multiple sources have said that the mass vaccination centres, which have mostly been used to deliver the Pfizer jab, in Cwm Taf Morgannwg would close.
On Facebook, the Plaid Cymru MS for the Rhondda Leanne Wood said “the vaccination centres are going to be closed for two weeks and they will be reopened at the end of the month the beginning of March”.
“This is something that was known about two weeks ago, it’s been planned for. The time is being used effectively in order to repurpose the vaccination centres, and the vaccinations that are available during this next two week period will be delivered through the GP surgeries,” she added.
Pontypridd Labour MS Mick Antoniw confirmed he understood the situation to be the same.
“It was something we were expecting,” he said, citing changes to boost production at Pfizer.
“In two weeks the vaccination centres will reopen,” he said. “Hopefully there will be increased supply of Pfizer.”
On Facebook, the Labour MP for the Rhondda Chris Bryant said that while progress so far has been “brilliant, it’s a shame that the lack of supply of the Pfizer vaccine for the next two or three weeks means that the mass vaccination centre is going to have to close temporarily”.
However, officials say they have sufficient stocks of Pfizer vaccine to significantly increase the number of second doses next week, as those who had a first dose in December are now due for their next injection.
A Welsh Government spokesman said: “Over the next couple of weeks, we are expecting a slight reduction in the amount of vaccines we will receive from the UK government – this is a planned and expected change in supply that will affect the whole of the UK.
“We have factored this into our plans and it will not affect people’s appointments or delay when people are due to get their second dose. The supply of vaccines is expected to ramp up significantly from the beginning of March.
“Every dose of vaccine we receive will continue to be delivered immediately to all those who need it. Our vaccination teams continue to do an incredible job to vaccinate everyone as quickly as possible.”
The UK government is procuring the vaccine for all four home nations.
A spokesman for the Westminster administration said: “We are confident that the steady, regular supply of doses will continue to support the vaccine rollout in the weeks ahead.
“If you get called for a vaccine, please continue go to your appointment.”
At the end of January, the UK vaccines minister Nadim Zahawi warned that new manufacturing processes meant supply was “lumpy and bumpy, it gets better and stabilises and improves going forward.”
The health board which covers Rhondda – Cwm Taf Morgannwg – was also asked for comment.