Up to 150 people could be in intensive care with Covid by the end of November, the Taoiseach has warned.
Micheál Martin also said he believed there could be an annual vaccine against the virus in the future and added that he could not predict when the country would return to normal following the pandemic.
In an interview with Newstalk FM, Mr Martin said there was concern about the growing number of Covid cases in the country.
On Friday, there were a further 2,466 confirmed cases, with 457 patients in hospital, 90 of those in intensive care units.
The Taoiseach said: “There are a lot of things going on. First of all, we are in a much different space than we were last year in the sense that we have vaccination and 93 per cent of the population have been fully vaccinated.
“There is concern out there, and I am concerned about the rising numbers.”
Asked about Nphet modelling for case numbers over the winter, Mr Martin said: “There is the optimistic model, there is the pessimistic model.
“You could be looking at up to 150 in ICU by the end of November. That would be serious in terms of the wider impact on the health service.
“But if we all collectively behave, what I mean by that is watch ourselves, be a bit more cautious about how we go about in congregations, we can pull this back.”
The Taoiseach said antigen testing and booster vaccines both had a role to play in combating Covid.
“My own view is that, given where we are now, I think antigen has a role. Some sectors have rolled it out effectively, I know there have been trials in universities.
“When people were fully vaccinated, there was a phase when people felt they didn’t need to do any tests at all. We now know if you are vaccinated it doesn’t mean you can’t get infected.
“The antigen has a role in that respect, but it is a role that supplements PCR tests, and they are both working together.
“Boosters will work and will give the extra protection that people require. The research is increasingly showing that.
“For the over-60s, I think this will be significant in preventing high case numbers.”
Mr Martin continued: “I actually think into the future we will be looking at an annual Covid vaccine for the time being, just like we have the flu vaccine.
“Science, in the end, and medicine will catch up with this virus and in the meantime we’ve got to use all of the weapons in our armoury to try and hold it at bay.”
Mr Martin said he had always felt that this winter would be a key stage in the battle against Covid.
He added: “It is very difficult to predict with Covid because we have to watch for any potential mutations and new variants, that is always a worry.
“It is very, very difficult to predict when we are going to return to the kind of normality that we experienced befor the pandemic. I always felt that we would have to get through this winter.
“There are different phases of this pandemic. We are now in a new phase with a fully vaccinated population, boosters and so on.”