The Health Minister Stephen Donnelly says Ireland is moving closer to an all-island approach to tackle the coronavirus.
Ireland is going back into a level five lockdown from midnight on December 24th until January 12th.
However there will be a number of specific adjustments to the restrictions, and certain arrangements will apply during the Christmas period.
A travel ban from the UK has also been extended until the end of the year.
It comes as cases of a new coronavirus strain have been spreading rapidly in Britain.
The mutation - known as VUI-202012/01 - is said to be up to 70% more infectious than the original strain because it has a much bigger viral load.
However there are no travel restrictions in place between Britain and Northern Ireland - with concerns people can then take trains and buses from Belfast to Dublin and other places.
Minister Donnelly told The Hard Shoulder the Irish Government is playing its part, but that there are "unique political and cultural considerations".
"My view has always been, and I think most people's view is, that the disease couldn't care less about the Battle of the Boyne or anything else.
"Ultimately the closer we can get to an all-island response to this the better."
He said the Government and Stormont Executive have "moved closer today".
"The Stormont Executive is moving on the 26th, as are we, they're putting in place very serious measures as are we from the 26th.
"Later this week it will be closer".
However he said any travel ban between Northern Ireland and Britain is subject to "unique political and cultural considerations there".
"All we can do is put in place what we think is appropriate here in the Republic, and that is the decision we made today".
Restrictions 'have saved lives'
Minister Donnelly admitted that the re-imposition of restrictions was "a very difficult decision".
But he said the situation has been changing rapidly.
"This day last week it was 329 new cases [of coronavirus] - the number that's going to be announced later today will be more than 900".
"The second thing is our doctors are very concerned about this new strain, this new variant that's been found in England".
And he said people's efforts have saved lives.
"Because of what your listeners have done, because of what the people have done over the last number of months... what it means is that there are hundreds and hundreds of men and women around Ireland right now... who are alive, and who are going to be having Christmas with their families because of what everybody has done".
December 30th vaccinations
And Minister Donnelly said vaccination will start here on December 30th, after it was approved on Monday.
"We're going to receive our first shipment on the 26th, on Stephen's Day, and our plan is to begin vaccinating people on the 30th of December."
"We're going to get just slightly less than 10,000 doses in the first shipment, but then probably - more importantly - from the first week of January, our expectation is to receive several tens of thousands doses of the Pfizer vaccine per week."
"Obviously we want that to ramp up, then".
He also said the European Union has moved up its decision date for the Moderna vaccine.
"We would then, as with the other European countries, start receive doses of Moderna", he explained.