NPHET has told the Government that it will become increasingly difficult to maintain the level of suppression of Covid-19 that has been achieved since the New Year.
Dr Tony Holohan advised the Minister for Health that NPHET expects a large number of additional deaths from the virus in the coming weeks.
In its letter to Stephen Donnelly on 21 January, NPHET said the country remains in a very vulnerable position despite great progress in recent weeks.
It warned that "we will all find it challenging to maintain the very low levels of social contact and adherence to social distancing and hygiene measures required to maintain suppression".
The letter said it is likely that the effective reproduction number will drift upwards in the coming weeks.
It also forecast that the variant will become increasingly dominant over the next 3-6 weeks and this will drive up the reproduction number.
Health Service Executive CEO Paul Reid said there has been a modest decrease in the number of patients in hospitals, saying it is the "first hopeful sign in many many weeks".
He said he really does hope it is the start of a trend.
However, Mr Reid said our health care system will not see the benefits of this for some time to come and for now we have to continue with the unrelenting pressure on our services across the board.
It continues to be a health care system continuing to battle and to work hard to protect and save lives, he said.
Many patients in hospital will need a sustained period of time in care and rehabilitation before they are well enough to be discharged, he said.
Some of the most vulnerable groups continue to be at high risk, he added.
Mr Reid said that thankfully the HSE is starting to see a return to work by staff who had been unable to attend due to Covid-19 positive or contact with positive cases.
However, he said, it is still at a high level of 5,500 absent but that is down from 6,600 last week.
In terms of ICU beds, Mr Reid said that the capacity overall remains too close to a tipping point for there to be any level of comfort.
He said there are 330 patients overall in our ICUs, including non-Covid patients, and that leaves just 18 intensive care beds, "which is extremely tight".
The feedback from the clinical team, Mr Reid said, is that patients are presenting much sicker in this wave and spend longer in ICU.
The briefing heard that antigen tests will be provided to acute hospitals from tomorrow and also, as of tomorrow, the testing of close contacts of a positive Covid-19 case will be reinstated.
It comes as the latest figures from the Health Service Executive show there are 1,620 people hospitalised with Covid-19.
That is up slightly on last night's 8pm figure of 1,598, but down on yesterday morning's number of 1,727.
The latest available figures show there are 216 patients in ICU.
Speaking at a media briefing this afternoon, the HSE CEO Paul Reid said that the situation in ICU was "too close to a tipping point".
In relation to ICU, Paul Reid says the overall capacity remains "too close to a tipping point". He says there are 1,620 Covid patients in hospital, 216 of whom are in ICU. He says there are 18 free ICU beds across the country | https://t.co/zUowRQ0yHI pic.twitter.com/HefWJl5PgI— RTÉ News (@rtenews) January 28, 2021
In Northern Ireland, a further 13 coronavirus deaths have been recorded, 11 of them occurring during the past 24 hours.
It takes the official Department of Health death toll to 1,792.
There are 592 new cases from tests on 2,992 individuals. 768 confirmed patients are in hospital, with 67 in ICU, 57 of whom are on ventilators.
The average 7-day infection rate per 100,000 for Northern Ireland is 216.1, the lowest it has been since 22 December.
The Stormont Executive is today expected to approve a proposal to keep schools in Northern Ireland closed until 8 March at the earliest.
Additional reporting Mícheál Lehane, Eileen Magnier