Both the AstraZeneca and Johnson & Johnson vaccines are to be made available for all adults, regardless of age.
NIAC made the recommendation to Government last night.
Young people will get a choice of whether to take one of the two vaccines or opt for mRNA vaccine (Pfizer or Moderna) instead - all subject to supply.
The two jabs had previously only been given to those over 50, amid the concerns over very rare cases of blood clotting.
However, the Taoiseach last week said the 'balance of risk' had changed due to growing concerns over the Delta variant of COVID-19.
Ireland's also expected to be left with tens of thousands of doses of AZ and J&J vaccines once older age groups are vaccinated.
The gap between doses of AstraZeneca is also set to be cut in half - from eight to four weeks.
This would allow many more people in their 60s to be vaccinated faster.
Tony O'Brien, former director-general of the HSE, says both of NIAC's recommendations are really positive.
He said: "They're a solid reaction to the emergence of the Delta variant in Ireland.
"They're in line with the European Centres for Disease Control recommendations, and they will enable us much more rapidly to increase the number of people who are getting access to vaccines at a time when we need that most."
Speaking on his way out of last night's Cabinet sub-committee meeting, Green Party leader Eamon Ryan said the recommendation is good news.
He said: "It is flexibility, and it will be up to individuals - subject to consent.
"It will also be subject to availability of AstraZeneca and Johnson & Johnson, neither of which have been the most reliable in terms of supply."
However, if future supplies arrive as expected, Minister Ryan said the change will give many younger people the option of getting vaccinated earlier than expected.
It comes as Cabinet meets today, with ministers expected to delay the return of indoor dining due to concerns over the Delta variant.
