Half of the 60 patients in intensive care units with Covid-19 are under the age of 55, the Chief Medical Officer has said.
Dr Tony Holohan was speaking after the Department of Health reported 1,592 new cases of Covid-19 with 318 patients in hospital, an increase of four on yesterday.
The number of people in ICU is up one overnight to 60.
Dr Holohan said: "Over the course of the last seven days, 32 people with Covid-19 were admitted to critical care facilities and today, there are a total of 60 people with Covid-19 receiving critical care.
"The median age of those in ICU is 55 - this means that 50% of the patients currently in ICU with Covid-19 are aged less than 55 years.
"Over the weekend, we reported that the number of newly confirmed COVID-19 cases in hospital in a single day had reached a level not seen since mid-February this year.
"Unfortunately, all of this indicates that we are still not at the peak of this wave of Covid-19 and that many people continue to experience severe illness due to [the virus]."
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Dr Holohan continued: "While our vaccination programme continues to offer great hope, at this point in time, only 53% of 16 to 29 year-olds are fully vaccinated. This age group continues to account for the highest incidence of Covid-19 in our population.
"Anyone who is eligible to receive a vaccine, should do so as soon as possible. It is vital that all of us complete our vaccination schedule - you will be fully protected 7-14 days after your second dose."
The CMO urged people to "consider each activity you take part in for its level of risk".
He also advised: "Continue to regularly wash hands, wear a mask when appropriate, keep your distance and avoid crowds.
"Manage your social contacts and choose outdoors where possible for meeting others. If you have symptoms of Covid-19, however mild, self-isolate immediately and arrange a test through the HSE or your GP."
In Northern Ireland, 1,320 new cases of Covid-19 have been reported in the past 24 hours along with nine deaths.
To date, 2,414,189 vaccines have been administered in the region.
Meanwhile, an ongoing rise in Covid-19 case numbers could impact on elective and delayed procedures in hospitals, with bed capacity reducing in recent days, the Heath Service Executive's Chief Operations Officer has said.
Anne O'Connor said there has been a significant increase in the admission of Covid-19 positive patients to hospitals since Saturday, rising from 259 patients then to 318 today, which is the highest figure since 29 March.
There are 60 patients with coronavirus in ICUs, an increase of one on the same time yesterday.
It is the highest figure since 6 April.
Speaking on RTÉ's News at One, Ms O'Connor said there is a concern around growing numbers in hospital and intensive care units, and "the system is coping...but it's not without its challenges".
4% of children test positive for Covid-19
Meanwhile, an assessment of data by the Health Service Executive has shown that 4% of children under the age of 18 tested positive for Covid-19 since 1 March 2020.
The epidemiological review found that the percentage of close contacts of a confirmed case that subsequently tested positive for Covid-19 was significantly lower in schools when compared to the outside population.
Over the course of the academic year, 44% of all schools nationally required a public health risk assessment and close contact testing.
Testing of identified close contacts under the schools pathway was done at 1,737 schools between August 2020 and July this year.
More than 100,000 members of the school community, representing 10% of that population, were tested as close contacts.
Elsewhere, gardaí have said they are making inquiries into a licenced premises near Croke Park for alleged breaches of Covid-19 regulations as people gathered for yesterday's All-Ireland hurling final.
In a statement, gardaí said they conducted a number of inspections at licenced premises in the Croke Park area yesterday.
It came on the foot of its policing plan for the final and reports of anti-social behaviour and a lack of social distancing among crowds, they said.