Taoiseach Micheal Martin warned that Omicron is of "serious concern" ahead of a crunch NPHET meeting later this week.
Chief Medical Officer Dr Tony Holohan will lead a hugely important meeting of the group on Thursday with less than two weeks to go until Christmas Day.
It comes after another eight cases of the Omicron variant were detected in Ireland on Monday, with the CMO warning “we are hoping for the best while preparing for the worst.”
Dr Holohan said NPHET estimates that 11% of cases are now due to the Omicron variant, an increase from less than 1% only one week ago.
And speaking ahead of a Cabinet meeting at Dublin Castle on Tuesday morning, Taoiseach Micheal Martin has said there is "serious concern" over the new variant - but refused to speculate on what new measures may be needed.
He told reporters: "We need everybody on board now, all hands on deck, in relation to the booster campaign because Omicron is of serious concern, and we do know the booster can give serious protection.
"Secondly I think people have adjusted well over the last six weeks, the way people have adjusted behaviour has impacted on stabilising hospital numbers and case numbers and I think people deserve credit for that.
"I think generally people are adjusting behaviour and that is important. And anything else is just speculation at this stage, but given the nature of Omicron we are in ongoing contact and engagement with public health.
"But the focus in the last couple of days has been on the booster campaign, working out the most effective ways we can expand it, and get more people jabbed as quickly as we possibly can."
Meanwhile, CMO Dr Holohan said on Monday that another 4,688 new Covid-19 cases have been confirmed here.
He said: “We are reporting a further 8 cases of Omicron variant, confirmed by whole genome sequencing, bringing the total confirmed in Ireland to 18.
"Possible Omicron cases can be identified by the number of PCR results with 'S gene target failure' - just as we did when the alpha variant emerged a year ago.
“Using this methodology, we estimate that 11% of cases are now due to the Omicron variant, an increase from less than 1% only one week ago.
“While evidence on disease severity and immune escape is still emerging, it is clear this variant is more transmissible.
“We are hoping for the best while preparing for the worst.
“Over the coming days and weeks global health authorities will learn more about this variant and the risks it poses.
“In the meantime, we continue to have confidence in the basic measures to reduce transmission.”
A statement from NPHET also said: “The proportion of cases that are Omicron is now rising exponentially and it is likely that there is now widespread community transmission of this variant.
“It is likely that the proportion of cases due to the Omicron variant will increase very rapidly over the coming days.”
