There have been 4,022 further confirmed cases of COVID-19 in Ireland.
The Department of Health says there are five additional cases of the Omicron variant here - bringing the total number to six.
The five-day moving average of cases stands at 4,374.
The discovery of these cases follows whole genome sequencing.
As of 8.00am on Thursday, 530 patients are hospitalised with the virus - of which 115 are in ICU.
Dr Tony Holohan, Chief Medical Officer, says more Omicron-suspected cases are being investigated.
"There are now six confirmed cases of the Omicron variant in Ireland.
"A number of other probable cases are under investigation.
"Although this is a new variant, our early understanding gives us confidence that a booster dose of COVID-19 vaccine will offer good protection against Omicron and Delta infection."
HSE chief clinical officer, Dr Colm Henry, has also said it is likely more cases will be confirmed in the coming weeks.
"I've no doubt there will be further cases, no doubt.
"There is a marker for this, but it's not absolutely specific - that's the S gene dropout.
"And at this point in time, quite a number of S gene dropouts are being investigated and being sequenced.
"I've no doubt many of those will be confirmed as Omicron cases", Dr Henry said.
Dr Holohan says it is 'heartening' to see the large numbers of people wanting to be vaccinated.
"Our current wave of disease continues to be driven by the Delta variant of COVID-19.
"We know that the public health measures we are so familiar with will break the chains of transmission of Delta, and we are confident they will work on Omicron.
"Please continue to layer up on the public health advice by getting vaccinated and boosted, reducing contacts, wearing masks, keeping distance, opening windows and cleaning hands regularly."
He adds: "It is heartening to see the large numbers of people who attended walk-in vaccination centres today to receive their COVID-19 booster dose as soon as it became available to them.
"If you are eligible for a booster dose, then please do not wait until after Christmas to receive it.
"You will begin to receive the benefit of your booster protection within seven days of receiving your third dose.
"This means that anybody who receives their booster vaccine this week or next can be confident in the protection the booster will offer as we move closer to the Christmas period."