People in their 50s may get their boosters earlier than planned.
The cohort was due to start getting appointments from mid-December, but the HSE now says they may begin to be issued sooner.
Boosters will initially be administered by appointment only but its expected walk-in clinics will be rolled out at a later stage.
Infectious Disease Specialist at the Royal College of Surgeons Ireland, Professor Sam McConkey says the booster campaign is gaining momentum.
"There was a lull in vaccines from August to October, and now in retrospect we should have been boosting the folk that were vaccinated in January/February in September and October.
"We can't change the past, but now I think the booster campaign is really taking off and everyone is doing it."
