The Cabinet will consider further measures to stem COVID-19 cases, including working from home, when it meets on Tuesday.
On Monday night the Cabinet Subcommittee heard up to 500 people with the virus could require ICU admission by next month, under a worst-case scenario, in new NPHET modelling.
It is believed the modelling suggests the peak will not be until some time in December, with the health service struggling to cope in the worst-case scenario.
In the most optimistic scenario, it warns that nearly all routine and elective surgeries could be curtailed in coming weeks.
HSE chief clinical officer - Dr Colm Henry - has said while it is "difficult" to put a number on a critical figure of ICU admissions, he believes 150 would be significant.
"This past weekend, we've seen our intensive care units - particularly in the Dublin region - under serious pressure", he told Newstalk Breakfast on Monday.
"Having to cancel other operations and having to exchange patients between hospitals - and having to provide a form of intensive care outside intensive care settings too.
"What you see is an overheated healthcare system at the moment.
"Intensive cares - yes the numbers if it got to 150, certainly would be very very difficult to see us providing the whole range of care at numbers well below that, I would say."
A further 4,570 cases of COVID-19 were reported here on Monday.
There were 622 patients hospitalised with the virus, with 117 of these in intensive care.
Ministers will consider the need for Digital COVID Certs to access gyms, hairdressers and barbers, the wider use of antigen testing and a booster programme for those aged 50 and over.
NPHET has also proposed that people who regularly engage in "higher risk activities" should consider self-testing on a regular basis.
This would be a minimum of twice weekly, spaced out by three days, for activities such as going to bars, restaurants, nightclubs, the cinema, multi-household visits, playing indoor contact sports and car sharing.
While Health Minister Stephen Donnelly said on Monday he was expecting advice from the National Immunisation Advisory Committee (NIAC) on rolling out booster vaccines to younger age groups.
"The evidence for the boosters is incredibly strong. We have about 1.4 million already greenlighted for the boosters.
"I am working with the HSE - it's all hands on deck in terms of getting these boosters out."
He added that NIAC advice should mean "a significant additional number" of people will be able to get a booster.
