The Taoiseach has confirmed over the 70s will be offered the Pfizer and Moderna vaccines, rather than AstraZeneca.
It follows a recommendation from the National Immunisation Advisory Committee.
The group said that the two mRNA vaccines - Pfizer and Moderna - are preferable for use in the elderly.
The Taoiseach says the covid-19 vaccination rollout plan now faces significant logistical challenges.
He told the Last Word that will result in a change to the operation of the vaccine rollout.
Micheal Martin said, "it will be a significant logistical challenge to the Health Service Executive", but they are working through the implications.
The Taoiseach said the plan to start vaccinating over 70's will start on February 15th as planned, but it will happen with the Pfizer and Moderna vaccine.
He says it will mean that people in cohorts 4,5, 6 and 7will be able to come forward in the plans to rollout the AstraZeneca vaccine.
