The Department of Health has reported 7,333 new cases of Covid-19.
It said there were 410 Covid patients in hospital, down ten on yesterday. There are 107 in ICU, up two from yesterday.
Today's case figure was the highest reported since early January.
Chief Medical Officer Dr Tony Holohan said: "Recent international experience and the rapid spread of the highly transmissible Omicron variant here means we can expect to see a large number of cases over the next short period of time.
"We all remember the call to 'flatten the curve' in the early days of the pandemic - we have successfully driven down incidence of disease in the community before - we can and must now work together to do it again.
"By choosing to act safely right now, together we can limit the impact this disease will have in the weeks to come and in doing so, we can protect the vulnerable, prevent unnecessary deaths and ensure the continued operation of our healthcare system and other essential services."
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Deputy Chief Medical Officer Dr Ronan Glynn said the Omicron variant posed a "significant threat" to a safe Christmas and new year.
He said: "Over the coming days please think about each of your social contacts and consider whether now is the time to be meeting with them.
"Meet up outside where possible and avoid all crowded settings.
"If you have symptoms please isolate immediately and arrange a PCR test - do not go to work and do not meet up with other people.
"If you are identified as a close contact it is vital that you restrict your movements."
In Northern Ireland, a further five patients who had previously tested positive for Covid-19 have died.
Another 2,075 confirmed cases of the virus were also notified by the Department of Health.
Meanwhile, people aged in their 40s in the Republic will be eligible to get Covid-19 booster vaccinations from tomorrow.
Those in the 40-49 age group will be able to access the booster vaccines in vaccination centres, GPs and pharmacies.
Booster vaccinations for this cohort had originally been slated to begin from 27 December, however that has now been brought forward.
HSE Chief Executive Paul Reid has encouraged people to access a booster vaccine at the earliest opportunity.
We're bringing forward the 40-49 ages for booster vaccines to now commence from tomorrow (Sunday 19th Dec). Please take the earliest opportunity to do so via Vaccination Centres (incl walk-ins), GPs (they will contact you) or contact your Pharmacy. @HSELive
— Paul Reid (@paulreiddublin) December 18, 2021
Minister for Health Stephen Donnelly announced the acceleration of the vaccination campaign following an announcement by Government of new restrictions, which will see bars, restaurants and indoor events close at 8pm starting on Monday.
Under the measures, all restaurants and bars excluding takeaways or delivery services, must close at 8pm and there should be no indoor events after this time.
However, there is an exception for weddings, which can take place after 8pm with a capacity limit of 100 guests. Religious service are also exempt.
For indoor events earlier in the day, attendance should be limited to 50% of venue capacity or 1,000 people, whichever is lower.
Attendance at outdoor events should be limited at 50%, or 5,000 people, whichever is lower.
There are no changes to the number allowed for household visits, which will remain set at four households.
The Taoiseach said it will take time to understand the full impact of the Omicron variant.
Mr Martin told RTÉ's Brendan O'Connor programme that the Government cannot afford to wait to see how the situation evolves.
He said that that he was "very worried about Omicron", but that how severe the variant is in terms of requiring hospital admissions and ICU treatment remains "the great unknown".
The chair of NPHET's Irish Epidemiological Modelling Advisory Group said Ireland should expect a lot of infections from the Omicron variant.
In a lengthy thread on Twitter, Prof Philip Nolan said that a smaller percentage of these infections will be severe.
He said: "However, the growth advantage of Omicron is large, so a large wave of infection is likely, and a small percentage of a large number of infections is a large number of severely ill people requiring hospital or critical care."
Prof Nolan added: "Omicron will be a very significant challenge, but we are acting early, quickly and comprehensively.
"If we take a booster vaccine when offered, significantly limit contacts, mitigate risk, self-isolate if symptomatic and restrict movements if a contact, we can get through it."
Omicron will be a very significant challenge, but we are acting early, quickly and comprehensively. If we take a booster vaccine when offered, significantly limit contacts, mitigate risk, self-isolate if symptomatic and restrict movements if a contact, we can get through it. 1/22 pic.twitter.com/221nBd605Z
— Professor Philip Nolan (@PhilipNolan_MU) December 18, 2021
More:
Pubs, weddings, concerts: New restrictions explained
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The Irish Medical Organisation (IMO) has notified GPs that they will receive a mix of the two recommended mRNA vaccines, Pfizer and Moderna, for the booster programme.
In an email to GPs, the IMO said significant levels of orders have been placed and deliveries are already underway and scheduled until Thursday 23 December.
"Given the level of stock required by the overall booster programme including General Practice and the necessity to distribute same in short order in the next week, there will be blended stock of the two mRNA vaccines," the correspondence said.
GPs were notified about what types of vaccines they will receive after the close of business yesterday.
However one GP has told RTÉ News that the mix of vaccines is a "big headache for their already overstretched administration system".
