The head of the HSE says he is 'quite nervous' of the impact patients with COVID-19 could have on other parts of the health service.
Paul Reid was speaking as 437 people with the virus are in hospital, and 88 of those are in ICU.
He told Newstalk Breakfast he expects those numbers to increase.
"We do expect that to rise this morning, and particularly rise throughout the weekend.
"88 people in ICU, which is a rise of about 27% over the last week in terms of ICUs.
"So our concern is particularly what happens over the coming weeks because, as we all know well by now, there is a lag effect between high levels of case numbers and the timeframe that that takes to turn into hospitalisations.
"We're managing, but quite under stress in a number of hospitals at the moment".
He says this relates to the impact of COVID-19 cases, as well as RSV and other indications of flu.
But Mr Reid says he is nervous over the impact COVID-19 could have on other health services this winter.
"I'm quite nervous as we head into the winter.
"If we look at the projections and the modelling, which are not off the Richter scale from NPHET, looking in the coming weeks they would indicate potentially 1,000 people with COVID alone in hospital, and potentially 150 people in ICU.
"Now 150 people in ICU takes up 50% of our capacity, so there's no scenario in which we can reduce our capacity by 50% and not impact on elective care".
'Focus on unvaccinated 8%'
And he says the HSE hopes to target the 8% of people who have not yet come forward for vaccination.
He says this includes groups such as the Travelling community, college students and meat plant workers.
"Throughout this week and next week we're going to have a range of campaigns and initiatives for people to come forward for vaccination with our walk-in clinics again.
"And also communications campaigns in terms of women who are pregnant and people who have concerns over fertility, non-English speaking people.
"We've quite a range of initiates to focus in on that 8%".
And he says more vaccinated people are becoming symptomatic.
"We are seeing more vaccinated people becoming symptomatic.
"In simple terms, it really is reverting to - and all of us we're spending more times indoors, we're spending more people socialising and working at work [sic] - it's really reverting back to the basics that have worked for us and can turn this around".
This involves hand cleanliness, mask wearing and social distancing.
He says as well as people, businesses and authorities have an obligation to 'up their game' around measures and checking COVID-19 Certificates.
"I think it's not just the transport sector, it's not just the airports, it goes for all of the industry, all of sectors.
"With the vast amount of people who are now out in retail units, in service industry - thankfully - it doesn't take a whole lot of actions to make a big difference."
And Mr Reid says he is 'anxious' to see healthcare workers receive a COVID-19 booster vaccine soon.
Around 1,800 healthcare staff are out of work at present with COVID-related issues.
The National Immunisation Advisory Committee (NIAC) has recommended over-60s receive a booster jab, but not healthcare workers yet.
"I've a concern for a few elements in relation to staff, but the health service in general - we are seeing more outbreaks emerging in healthcare settings.
"And that's always a concern, and it's an inevitable factor when it's so high in the community that we will get breakthroughs in the healthcare settings.
"But equally that's an indication for me that we ensure the strength and immunity of our healthcare staff as well and their levels of protection.
"We do have a significant proportion of staff out - not all frontline healthcare workers - but a significant element.
"And that would be an actual fact when you see the levels in the community.
"I would be really anxious, as soon as possible, that we can get our healthcare workers vaccinated.
"I'm just really anxious that we keep those levels of protection strong - not just for themselves, but equally for vulnerable people that we support".