Another Covid-19 vaccine is expected to be approved for use throughout the European Union today.
The European Medicines Agency (EMA) will continue its assessment of the Moderna jab when it meets later.
Ireland has ordered 875,000 doses of the Moderna shot, but delivery will not commence until approval has been granted.
The roll-out of the Pfizer/BioNTech vaccine has commenced here, with healthcare workers and people over 65 resident in long-term care facilities the first to be vaccinated.
Unlike the Pfizer shot, the Moderna vaccine does not need to be stored at ultra-low temperatures, making its distribution easier for more remote settings.
Immunologist Lara Dungan says once it gains approval, the doses can be roll-out very quickly.
"Looking at the evidence with the Pfizer/BioNTech vaccine, that was approved on December 21st by the EMA, we have proven that we can get vaccines into this country very quickly and we can get it into people almost as quickly.
"So far it's been really good for the vaccination strategy and I think the Moderna vaccine, if and when it's approved today, will get to Ireland very quickly and I do think that we will start rolling it out very soon after that."
If the Moderna vaccine is approved today, there will be four remaining vaccines in development which the EU has signed Advance Purchase Agreements (APAs) for.
As an EU member state, Ireland will have access to 1.11 per cent, or 14.4 million doses of the EU's total vaccine stock.
AstraZeneca, CureVac, Sanofi/GSK and Jassen Pharmaceuticals (J&J) are the other vaccines which the EU has signed APAs for.
