Wales' health minister says he is "hopeful" Covid vaccine targets can be met.
Vaughan Gething said there had been a "significant increase" in doses sent out, with 20,000 delivered daily over the past few days to health boards.
It is hoped 70% of the over-80s will get the first dose by Monday.
Meanwhile, a health board said a fake social media post prompted "huge volumes of visitors" to turn up without appointments at one vaccine centre.
In a statement on Facebook on Sunday, Cardiff and Vale University Health Board said: "We understand that a post has been circulated on social media suggesting that, due to a number of cancellations, individuals falling into the over-70s cohort can turn up at our Splott vaccination centre today to receive a vaccination.
"We are now experiencing huge volumes of visitors and large queues which we unfortunately cannot accommodate.
"Appointments for over-70s will be starting from next Wednesday."
More than 264,000 people have received their first vaccine in Wales, according to latest figures.
The figures showed that 47% of people aged 80 and over had been vaccinated.
"If the supply is there, then we can deliver significant volumes of the vaccine," said Mr Gething.
"That does then mean we should be on schedule," he told BBC Wales Politics.
However, he said it was not yet clear if the weather would affect vaccination targets as four vaccination centres have been closed temporarily due to snow in the Cwm Taf Morgannwg health board area.
"I'm still hopeful that we will, although today's arrangements have been interrupted," he said.
"We won't be completely sure about the exact impact until later in the day."
Mr Gething went on to say he expected over-80s to have received their first jabs "in the coming days, and we are going to see over-70s invited for their appointments over this next week in every health board".
He said further vaccination centres were due to open, taking the total to 45 in Wales.
"We're going to be delivering second doses in the not too distant future as well so that infrastructure is important," he added.
Senior doctors in Wales have warned a delayed gap between the first and second dose of the Pfizer-BioNTech vaccine would be "entirely unacceptable and potentially dangerous".
The British Medical Association Wales (BMA Cymru) has joined calls for the 12-week wait to be halved.
Mr Gething said the Welsh Government had taken advice from health experts on its vaccination strategy.
He said: "You can provide a high level of protection with a first shot, and you make a choice between providing a much smaller number of people with excellent protection by giving them two doses, or with a much larger group of people with a higher level of protection by giving a single dose."