People in their 30s will be eligible for a booster vaccine from Wednesday.
The programme will also be opened to 16-29-year-olds who received the single-shot Johnson and Johnson vaccine.
The rest of the 16-29 age group will then be eligible for a booster vaccine by January 10th.
While many GPs are already giving booster vaccines to their younger patients, the extended rollout means pharmacies and mass vaccination centres will also be able to offer extra doses to all adults.
People can get a booster three months after their second dose.
Health Minister Stephen Donnelly said: “I am delighted to announce this acceleration of Ireland’s COVID-19 Vaccination Programme.
"As we face into a challenging period, it is important that all groups have the opportunity to be vaccinated with a booster to offer protection to as many people as possible."
It comes after two days where the HSE administered a record number of vaccines, with more than 100,000 boosters administered on both Tuesday and Wednesday.
Meanwhile, daily COVID cases are continuing to rise, with 7,411 new cases confirmed yesterday.
The rest of the booster programme will take place alongside the vaccination of children aged 5-11.
Children with a health condition or who live with someone at high risk of COVID-19 will start getting vaccines from January 8th.
That will then be extended to all 5-11 year-olds from January 8th.
Parents will be able to book a vaccination appointment online from December 28th.
Taoiseach Micheál Martin has said he knows it will be something parents think long and hard about, and that the Government will approach the issue "with sensitivity".
He said they will be "recommending strongly" that parents do get their children vaccinated, adding there will likely be separate vaccination facilities for children.