The head of the HSE says new guidance on Covid vaccines will pose "significant challenges" to the rollout to over 70s.
It's been advised that people in that age group should get the Pfizer or Moderna jab - rather than the AstraZeneca one.
Over 219 thousand people have received at least one dose so far - with around 8 thousand administered each day over the last week.
Locations where multiple GPs can vaccinate over 70s are being looked at - as the Pfizer and Moderna jabs are more difficult to store.
HSE chief executive Paul Reid says contingency plans are being finalised.