Over 500,000 Covid-19 bivalent vaccines have been administered since the vaccines were introduced on 3 October.
Adapted bivalent Covid-19 vaccine boosters include components of the original virus strain and the Omicron variant.
They are now preferentially recommended for all those eligible for a booster vaccination.
Almost three-quarters (74%) of doses are being administered by GPs and pharmacies participating in the winter programme.
Minister for Health Stephen Donnelly said that exceeding half a million bivalent boosters was a milestone in the efforts to ensure Ireland is prepared for a winter wave of Covid-19.
Latest figures show that as of 8am, there were 304 people in hospital with Covid-19.
Of these, 11 people with Covid-19 were being treated in intensive care units.