Health Minister Stephen Donnelly has said the issue around vaccines is not about supply, but timing.
He was speaking after the target of vaccines arriving up to the end of March was revised downwards - from 1.2 million to 1.1 million.
Minister Donnelly told Pat Kenny the issue is mostly from AstraZeneca.
"The figure we have always been planning to is 1.2 or 1.25, and that looks like it might be closer to 1.1.
"It's still obviously very high relative to the forecasts.
"The company that has been repeatedly revising down its forecasts is AstraZeneca.
"Moderna have been coming in pretty much on schedule, there was a bit of a wobble last week - but pretty much on schedule - though they're a relatively low amount.
"Pfizer to their credit, there have been a few wobbles, but by-and-large the supply has been the amounts that were agreed when they were agreed.
"The issue repeatedly has been AstraZeneca".
'No private sale' of AstraZeneca
He said Ireland has opted in to the full European Union allocation and top-up schemes.
"We've advanced purchased about 18.5 million doses - it's enough to vaccinate every man, woman and child in the country twice.
"So the issue isn't so much around supply, the issue is timing.
"Everybody wants to get this vaccine as quickly as possible".
Minister Donnelly said while they are in 'constant communication' with pharmaceutical firms, the European Commission and other countries, Ireland will be unlikely to stray from the EU model.
"The idea that there are other countries out there who are just going to give us their vaccines, before they vaccinate their own people, obviously doesn't hold up."
And he said while the Government has spoken with AstraZeneca, there is very little that can be done.
"We spoke to AstraZeneca who said very clearly there is no private sale, supply or distribution of their product."
Minister Donnelly added that no matter where the vaccine is manufactured, it would not make a difference.
"My understanding is what the pharmaceutical companies have done is shift other production to Ireland, to free up capacity to do the vaccine manufacture.
"But I think the important note out of this is even if it was all being produced in Cork or Dublin or Galway, it wouldn't increase our supply because we're part of the EU distribution".