The Taoiseach has warned that it's "inconceivable" that a new strain of Covid-19 – more infectious than what came before – has not already arrived in Ireland.
Micheal Martin said today that there are "risks" associated with inter-generational mixing over Christmas, adding: "The less congregation, the better."
Mr Martin's comments come as Ireland plunges into a third lockdown from tomorrow, with pubs and restaurants to shut from Christmas Eve amid soaring case numbers.
"Government had to move quickly in terms of the severity of the measures that we took yesterday, which will dismay many, particularly in the hospitality sector," he told Claire Byrne on RTE Radio 1.
"They've had a terrible year, in terms of opening, closing, reopening, closing."
The Taoiseach added that he knew what a big ask it was for people who have arrived from the UK in recent weeks to self-isolate, but added of the new strain: "Most people I speak to, who are experts in infectious disease, are telling me it is here.
"They're saying that it's inconceivable that it's not here."
In terms of the vaccine, he said the number of vaccine batches will be low in January and February, but will pick up "significantly" in March, April and May.
This morning, Dr Colm Henry, the chief clinical officer of the HSE, said anyone who came to Ireland from England, Scotland or Wales after December 11 should eat Christmas dinner in their room.
Dr Henry said the advice to these travellers – which was previously to restrict movements for 14 days – has now been upped to a requirement to self-isolate for the full 14 days.
This, he said, means people must stay "in their rooms at all times" except for absolutely "essential purposes."
"We know how painful this is for people who have waited so long to come home," he said.
But he added that it was necessary in order to "ensure that you are not the agent of transmission of this new strain."
