The European Commission says pharmaceutical firm AstraZeneca will deliver nine million additional doses of its coronavirus vaccine in the first quarter of this year.
This will see it deliver 40 million does in total.
European Commission President Ursula von der Leyen says it will also start deliveries "one week earlier than scheduled", calling the move a "step forward" on vaccines.
The company will also expand its manufacturing capacity in Europe.
It comes just days after the drug was granted authorisation in the EU.
In its recommendation, it said it should be used in people from 18 years of age - despite German experts advising not to give it to those aged 65 or over.
The vaccine is given as two injections in the arm, the second between four to 12 weeks after the first.
It follows comments on Friday by Health Minister Stephen Donnelly, who revealed that Ireland would receive doses of the drug a week earlier than planned.
He told Newstalk: "We've succeeded in getting it in a bit earlier. The contract was to get it in the week of the 15th of February.
"I can confirm now, for the first time, that it's been agreed that we will get it in the week of the 8th of February.
"It may not be the 8th, but the week of the 8th.
"So a week earlier: that means we can get it out, get it into people's arms and get people protected that little bit earlier as well".
Ms von der Leyen was speaking on Sunday, following a videoconference with the CEOs of the pharmaceutical companies that the commission has signed Advance Purchase Agreements with - including BionNTech-Pfizer, Moderna, AstraZeneca, Johnson & Johnson, Curevac and Sanofi.
The executive director of the European Medicines Agency (EMA), Emer Cook, also attended the call.
It follows an ongoing row over supply cuts, which nearly derailed the Brexit settlement in the North.
Plans were set out on Friday to block vaccine exports from EU states, which was met with anger from politicians on both sides of the Irish border.
Taoiseach Micheál Martin, who had spoken to President von der Leyen about the matter, welcomed the reversal from the EU.
He told Newstalk on Saturday that the swift action meant restrictions on trade were avoided.
He said: "I think [UK PM Boris Johnson] understands the importance of the Protocol and the need for the Protocol to work in the interests of what we all agreed.
"That's why it was so important that the European Commission reversed their decision last night.
"I think that gives sufficient space to the British Government not to have to respond in a hurried manner but rather to continue to engage with Ireland and the EU and with Northern Ireland politicians in terms of the fine-tuning of the protocol."
Brussels was expecting 80 million doses by the end of March at least.
But that was before the pharma firm said a production glitch meant it had it to slash its deliveries by around 60% - right down to 31 million doses.
Now it seems Commission President von der Leyen is settling for about half.
Ireland has been getting about 1% of the EU's total vaccine deliveries.
This announcement sees the Health Service Executive (HSE) in line to receive around 90,000 more doses.