HSE Chief Executive Paul Reid has said that Ireland will cease further deliveries of AstraZeneca and Janssen vaccines.
It comes as the EU focuses its efforts on acquiring mRNA vaccines.
Mr Reid said there is currently a strong availability of mRNA vaccines in Ireland and therefore further deliveries of AstraZeneca and Janssen will be suspended for now.
The HSE said it follows advice from the National Immunisation Advisory Committee which found that Ireland has "surer supplies" of mRNA vaccines, and appointments can be offered in a "timely manner".
In a statement it said that the decision was made in the context of the "risk posed by the Delta variant in conjunction with the availability of mRNA vaccines".
The HSE said it had requested a suspension of further deliveries of vector vaccines (AstraZeneca and Janssen) "to avoid any unnecessary build up and possible wastage of vaccines".
Mr Reid highlighted that the recent vaccine supply deal with Romania would see 700,000 mRNA vaccines delivered to Ireland in the coming weeks.
Meanwhile, the Department of Health has been notified of 1,758 new cases of Covid-19.
The number of people in intensive care units is 48, up five on yesterday.
There are 248 people being treated for the virus in hospital, up 19 since yesterday.
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Mr Reid said hospital numbers had increased six-fold in six weeks, but said the figures had to be viewed in context and stressed that the vaccination programme was having a significant impact.
"Vaccinations are working, they are reducing hospitalisations, they are reducing illness, ICU and mortality," he said.
"If you think back to January, we had 2,020 people in hospital and 212 people in ICU.
"We do have a concern with the rising numbers, rising everyday case numbers.
"We're now at over 2,000 and equally just seeing some rise in case numbers across all ages and across the whole country."
30,000 12-15 year-olds receive first vaccine dose
Around 30,000 children aged 12 to 15 received a first Covid-19 vaccine in the first two days of the rollout to that age group.
Mr Reid said 90,000 children in the cohort had been registered for a vaccine appointment by early this afternoon.
Some vaccines centres began to give jabs to 12 to 15-year-olds on Friday but the main rollout began in earnest yesterday.
The children, who need the consent of a parent or guardian to get vaccinated, are receiving Pfizer or Moderna jabs.
There are around 280,000 children in that age group in Ireland.
Mr Reid said he was not concerned at the uptake level so far and expected there to be continuous registrations over the coming two weeks ahead of the new school term.
Speaking on RTÉ's This Week, he also confirmed that children who are fully vaccinated would not have to isolate if they were identified as a close contact of a positive case within the school environment, as long as they were not displaying symptoms.
Mr Reid said those children who had not been vaccinated would still have to isolate.
Mr Reid said 81% of the adult population in Ireland was now fully vaccinated and 90% partially vaccinated.
He said the isolation policy for schools was aligned with public health advice for the population as a whole.
"You are more exposed if you are not fully vaccinated and you are highly more protected if you are vaccinated, so it's really aligned with the public health advice that we've put in place throughout," he said.
He also expressed concern at rising Covid-19 case numbers in Ireland. The 2,074 confirmed cases reported yesterday was the first time since January that the daily total had exceeded 2,000.
Mr Reid was also asked about inconsistencies around partner access at different maternity hospitals in Ireland.
He said he had asked senior officials, including Chief Medical Officer Dr Tony Holohan, to meet with patient advisory groups and advocates next week in an attempt to address some of the issues.
"We do want to find a shared pathway out of this," he said.
Mr Reid said: "The good news is we have a very good supply line to complete this age group asap because we have the supply line from the Romanian vaccines coming through, 700,000 over the coming weeks."
There will also be late opening times at vaccination centres, Mr Reid said.
"90% of the adult population (are) partially vaccinated and now 81% of adult population are now fully vaccinated."
On the return to school, Mr Reid said: "We're working with the Department of Education, our public health team on the whole process around return to school, but that will be one of the measures that we have in place, because people are much higher protected with vaccinations."
He said delivering the correct information to parents is essential at this point in the vaccination programme.
"If you are fully vaccinated and out of your vaccination period and you're fully protected, if you are a close contact you don't need to isolate if you are not symptomatic.
"If you're symptomatic you will be advised to isolate, but for people who are fully protected they don't need to isolate."
Chair of the Covid-19 vaccination taskforce Professor Brian MacCraith said another "significant milestone" in the vaccine rollout has been reached, with GPs and their practice teams administering two million doses.
Another significant milestone in the vaccine rollout reached today:— Brian MacCraith (@muirtheimhne) August 15, 2021
GPs & their practice teams have now administered 2m doses!
All of this was achieved on top of all of their other commitments.
Major congrats & thanks to @IMO_IRL @ICGPnews @PracticeNurses @todowd @DrNuala
Latest figures also show that 6.35 million doses of a Covid-19 vaccine have been administered in Ireland.
This includes 2.85 million second doses.
In Northern Ireland, 1,294 new cases of Covid-19 were reported today, along with three deaths.
There are 359 Covid-19 patients in hospital, including 44 in ICU.
Additional reporting PA