The head of the HSE says walk-in vaccination centres will continue this weekend in some 'high case' areas.
Paul Reid was speaking as 1,818 further cases of COVID-19 were confirmed here on Thursday.
While figures show some 124,000 of people aged between 12 and 15 have now registered for a vaccine.
It comes after the vaccine portal opened for that age group last week.
Mr Reid told The Hard Shoulder walk-in clinics are still being offered in some areas.
"Right now we are in a really strong position on supply of mRNA vaccines, which is what we're vaccinating now at this stage with - which is the Pfizer and Moderna vaccines.
"We have a number of walk-in clinics continuing throughout this weekend and into next week, and I would encourage - for over 16s - and some of those we're prioitising around areas where we're seeing high case levels of the virus".
He also suggested more walk-in centres will be used "at a point in time".
ICU figures
On those being hospitalsed with the virus, Mr Reid says the majority are unvaccinated.
"63% of hospitalised cases were over the age of 50, 31% of them hospitalised cases were between the ages of 19 to 49.
"And 6% of the hospitalised cases were of the ages of 0 to 18 - and that's the kind of mix that we're seeing.
"In ICU, 58% of the ICU cases are over the age of 50, and 42% are in the age bracket of 19 to 49.
"We're still seeing ICU admissions across all ages, and we're seeing a high prominence - between 78% and 80% - of people in ICU [who] haven't been fully vaccinated".
But generally, he says vaccines are continuing at pace.
"We are now at 6.5 million vaccines administered in total - so that equates to just about 84% of the adult population now fully vaccinated - and 90% partially vaccinated.
"So we're continuously chipping away and closing that gap.
"Very positively continuing down through the ages, with progress on uptakes between 16 to 17s.
"Since last week also on the 12 to 15-year-olds... we've approximately 125,000 of 12 to 15-year-olds registered for the vaccine.
"And about 75,000 have had administration already of the vaccine".
More vaccine deliveries
He says this is in line with trends in other age groups.
"It's kind of exactly what we are seeing as we have moved through the younger ages.
"That you see a reasonable, steady registration over a couple of weeks - and we would hope to see that, and expect, to see that continue.
"It's in line with the trend of the 16 to 17-year-olds also".
He says plans for Ireland to move away from using the AstraZeneca and Johnson & Johnson vaccines is an EU decision.
"The direction on that certainly didn't come from the HSE, it came from an EU steering board to individual countries.
"It's purely just because of the supply lines that we do have now of mRNA vaccines."
Earlier this week, the head of AstraZeneca in Ireland - Dan Wygal - told Newstalk the company's ambition was one of the issues it faced in the early stages of the pandemic.
"There's a few things, and it does relate back to the ambition itself... We're a particularly ambitious organisation, particularly when it comes to science", he said.
"We embarked on this partnership with the University of Oxford, and indeed it was an ambition that normally you would scope out for a period of years - trying to building a supply chain of this magnitude - and we did it in a matter of months.
"So a lot of it frankly was growing pains", Mr Wygal added.
But he is hopeful AstraZeneca can play a part in any future process.
Today we received our biggest weekly delivery of vaccines to this country of over 540,000 doses. This was hugely boosted by the first tranche of a total of 700,000 Romanian reallocated vaccines. It's key that we get to the smaller percentages of people now unvaccinated @HSELive pic.twitter.com/XCd3WczE7c
— Paul Reid (@paulreiddublin) August 18, 2021
On extra vaccines from Romania, which saw more than 540,000 arrive in Ireland this week, Mr Reid says a similar number will arrive here next week.
"There's a total of 700,000 of Pfizer vaccines... what we saw this week is some of that first delivery, along with our own projected delivery.
"And we'll probably see a similar volume of delivery next week again - so over over 500,000 being delivered next week again".
