The rollout of the booster campaign has seen as the health service up its defences against the spread of the Delta variant and the threat of the Omicron variant.
The European disease watchdog today warned that Omicron could become the cause of more than half of coronavirus infections in the EU “within months”.
It comes as the latest figures show that the Health Protection Surveillance Centre has today been notified of 4,163 confirmed cases of Covid-19.
As of 8am today, 545 Covid-19 patients were hospitalised, of whom 117 are in ICU.
Meanwhile, the HSE has confirmed that, last week, cases fell by 14.6pc among the over-85s, 18.8pc in 75-to 84-year-olds, and 8.3pc in the 65-to-74 age group.
The decline in cases is evidence of the booster shot benefits.
However, cases rose in two age groups, including the under-18s, whose infections rose by nearly 12pc, and also in 35- to 54-year-olds.
It comes as the HSE suggested that most people over 50 should be substantially boosted, or at least have an appointment scheduled, by the end of the year.
Damien McCallion, who is heading the booster rollout, said 85pc of the over-80s are boosted, as are 74pc of people in their seventies and around 100,000 of the 470,000 people aged 60 to 69.
Two-thirds of healthcare workers are boosted, as are 80pc of people with very lowered immune systems and 11pc of the medically vulnerable, whose vaccination started this week.
Mr McCallion expects the first deliveries of Covid vaccines for five- to 11-year-olds to arrive at the end of December, with more coming in January.
How soon they will be rolled out will depend on the recommendations of the National Immunisation Advisory Committee (Niac). An operational plan is being worked on.
HSE chief Paul Reid said the situation in hospitals has stabilised. However, he added that health authorities remain on alert for a potential "turn" after Christmas if there is another spike in Covid admissions coupled with flu and winter illnesses.
The HSE said more needs to be known about how easily the Omicron variant spreads and whether it impacts vaccines.
Figures show that unvaccinated people are still having a disproportionate impact on critical care and they are 11 times more likely to end up in intensive care than a fully vaccinated patient.
They are three times more likely to be hospitalised.
Just 6.5pc of adults are unvaccinated and in the last week there has been a significant rise in people coming for their first or second jab, he added.
Mr Reid said: "We now have 547 positive Covid patients in hospital, which is down about 8pc on last week.
"Over the past seven days there have been 345 admissions of Covid patients to hospital, which is an average of about 49 per day.
"In the 14 days to yesterday, 506 patients have been hospitalised to date. Of the 506, 40pc are aged 65 and over, about 40pc are aged between 35 and 64, 13pc are between the ages of 19 and 34, and 7pc are zero to 18 years of age."
Today, there are 117 Covid patients in intensive care, a fall of 11pc on this day last week and 2pc lower than a couple of weeks ago.
Hospitals are coming under pressure from admissions in recent days of non-Covid patients who are very sick.
HSE Chief Operations Officer Anne O'Connor said there is significant concern because ambulances bringing patients to hospital are so busy. This is a benchmark signalling the level of demand for emergency admissions.
"If we continue to work so much higher than our projected level, when we get to the end of December we will have cause for significant concern in terms of our unscheduled care activity,” she said.
"We are watching that and certainly our ambulance activity is very, very high, and we see that in terms of just the number of people who need fairly acute admissions to hospital."
Mr McCallion said yesterday was the busiest day for Covid testing, with 28,709 test appointments offered.
More pop-up testing sites are being opened including in Tuam, Rathdrum, Carlow, Navan and south Kildare.