Over 280,000 doses of the Pfizer / BioNTech vaccine are due to arrive in Ireland in a single delivery in early June, the Taoiseach says.
He said the delivery is due on June 2nd.
Micheál Martin said around 280,000 people are being vaccinated this week, with similar numbers expected next week.
A million doses of vaccines are set to have been administered this month alone.
The Taoiseach told reporters there's "good news all round" on the vaccine front, although stressed the goal of offering a vaccine to over 80% of all adults by the end of next month is still dependent on supply.
He said: “There’s still uncertainties around the AstraZeneca and Janssen supplies… some indications that Janssen may come short in their supplies. That said, Pfizer and BioNTech are really the star performers yet again.
“I think the largest volume will come in from Pfizer on 2nd June… I think about 280,000 plus in one delivery.
"That will happen every week in June. There'll be very, very strong momentum for this month and throughout June."
The vaccination programme has been continuing despite the ongoing impact of the cyberattack on the HSE.
The Taoiseach this evening said the Government does not know why the hackers who attacked the health service released a decryption tool.
This key gives the HSE access to the files it was locked out from in the attack.
Mr Martin said it will take time for security experts to roll out the tool, and "enormous work" lies ahead in rebuilding the system.
He reiterated that the Government did not pay any ransom in return for the decryption key's release.