There have been a record 20,554 further cases of COVID-19 in Ireland.
Latest available figures show there are 619 patients hospitalised with the virus, of which 88 are in ICU.
The five-day moving average of cases has jumped to 12,625.
Dr Tony Holohan, Chief Medical Officer, is again appealing to people to avoid mixing indoors.
"For the fourth time this week, we are reporting Ireland's highest ever number of confirmed cases of COVID-19.
"The most effective way to minimise the risk of any of us transmitting this virus to others is to avoid mixing indoors with people from other households.
"I know this is not the advice any one of us wants to hear, particularly in advance of New Year celebrations.
"However, given the current profile of the disease, it is essential that all of us continue to keep our social contacts as low as possible in the days ahead."
In the last 24 hours, 148 people with COVID were either admitted to hospital or received a 'detected' test result while in hospital.
Dr Holohan says hospitalisations at this level "are not sustainable" and are having a significant impact on the health service.
"It is important to note that these admission figures are increasingly likely to be driven by the surge in Omicron infection, which now accounts for over 90% of PCR confirmed cases in Ireland.
"Over 90% of people in hospital and intensive care with COVID-19 are there for the management of COVID-19 - less than 5% of those in hospital or intensive care have 'incidental' [asymptomatic, non-infectious] disease."
Dr Ronan Glynn, Deputy Chief Medical Officer, says even those boosted will be infected.
"Omicron is far more contagious than previous variants and incidence across the country is now much higher than at any point in the pandemic.
"Because of this many people, despite being boosted and having taken other measures to protect themselves, will be infected with SARS-CoV-2.
"However, their booster will protect the vast majority from serious illness or hospitalisation, and it will help to protect our health service and critical care capacity."
Dr Glynn adds: "To date, over two million people have received their booster - without this very significant uptake, the current impact on hospitalisation would be considerably worse.
"Please come forward and avail of your booster as soon as it is available to you.
"If you have not yet had any COVID-19 vaccine, it is never too late: please come forward and avail of it as, without it, you are at risk of very significant illness if you are exposed to the virus."
It comes as a consultant in infectious diseases has said there are many more positive COVID-19 cases in the community than figures suggest.
Dr Eoghan De Barra earlier told Newstalk we still do not know the full extent of COVID-19 infection.
"The testing system is completely full at the moment, I think we all know many people who've been up till midnight trying to get PCR slots.
"The system can't cope, and we don't have an idea of demand - at least the HSE doesn't release [to] us how many clicks they're actually getting to try to get slots.
"The 50% positivity rate is a vast over-estimate probably because of the number of people who are doing a follow-up on a lateral flow - an antigen test that was positive.
"So there are probably many, many more infections out there that either can't get a test, are not going to bother getting a follow on test, or indeed have such minimal symptoms that they're not going to get [a test]."
And he said it is likely people have the virus, but are unaware.
"We know on - I think - the 16th of December in London, one in 20 people in London was positive... so there are many more positive cases.
"So I think I'd echo Tony Holohan's comment that the likelihood is, if you're going to meet up with some people today some of them are positive - likely unbeknownst to themselves."