It follows updated advice from the National Immunisation Advisory Committee that people with weak immune systems should get an extra mRNA dose.
NIAC also updated its advice on mixing and matching shots, which's being facilitated at walk-in clinics this weekend.
HSE lead on the vaccination programme, Damien McCallion, says they're currently working to identify people who qualify for a third dose:
"Immunocompromised people with two doses will not get the same benefit as say someone who isn't immunocompromised, so this is a third dose to support their primary vaccination rather than a booster as such but in practical terms for us there are a very specific set of conditions and illnesses that have been recognised and identified by NIAC, and we're working goes through now in terms of trying to see how we will identify those people and offer them that third vaccine as part of their primary vaccination."
