People aged 30 to 39 can now get a Covid-19 booster vaccination, the HSE has said.
Those who are double vaccinated, are three months on from their last dose, and have not had coronavirus in the intervening period can get their booster jab at walk-in clinics, by booking online, or by appointment from Wednesday.
Boosters are also available to those aged 16 to 29 who received the one-shot Jansen vaccine, in line with guidance from the National Immunisation Advisory Council (Niac).
An HSE statement said:
People seeking booster vaccinations can attend walk-in clinics, or wait for a text message from the HSE offering a scheduled appointment.
Some pharmacies and GPs will also be offering booster jabs.
People are advised to take ID, such as a passport, driver's licence or Garda age card.
Those aged 30 to 39 should be offered a single dose of an mRNA vaccine, either Pfizer or Moderna.
The HSE said people can receive these vaccines "even if you got a different type (of) vaccine for your primary course".
People are advised that they must be three months on from their second dose, and that this will be checked at the vaccination centre.
Those who have been diagnosed with Covid-19 since their second vaccination should wait until three months after their positive test to get the booster.
People over the age of 40 will still be accommodated at walk-in clinics.