People who receive the first dose of their coronavirus vaccine from Monday will wait an extra week for their second dose.
The HSE plans to give people a second dose of the vaccine 28 days after the first, instead of 21 days which it says follows recommendations from the World Health Organisation and the National Immunisation Advisory Committee.
The change will apply to anyone receiving their first dose from Monday onwards, with the HSE saying it will allow them 'maximise our resources and vaccinate more people' as supplies arrive into the country.
A 21 day gap between jabs will continue to apply to anyone who has received their first dose already.
It comes as Tánaiste Leo Varadkar says Pfizer 'may be slowing down' its supply of its coronavirus vaccine.
However, he said it's unclear about whether the news will impact Ireland.
Norwegian authorities have today said a 'temporary reduction' in supply of the jab will affect all European countries, as Pfizer is reorganising its production efforts.
Norway's public health agency added that while the exact length of the temporary reduction is unclear, it means Pfizer will be able to increase its maximum production capacity in the longer term.
Mr Varadkar this afternoon said the "only constraint" on the rollout of vaccines here is supply.
He said Ireland has no control over when the EU approves vaccines for use, or how fast manufacturers can supply the jabs.
However, he said officials here are gearing up to get the vaccine into people's arms 'within days' of it arriving in the country.
It comes as new data shows Ireland has the highest daily vaccination rate in the EU.
Figures from Our World In Data reveal that Ireland has administered more vaccines per 100 people this week than any other country in the EU.
In a tweet, Health Minister Stephen Donnelly welcomed the news.
Thanks to our brilliant vaccination teams, for now we have the higest daily vaccination levels in the EU27. It won't always be like this, as member states get same per capita amounts of vaccine. But great we're moving quickly. 🙏👏👍 pic.twitter.com/DFR7amwlvi
— Stephen Donnelly (@DonnellyStephen) January 15, 2021
However, he warned that Ireland won't always be top of the table as member states get the same amount of vaccine per capita.
The Government earlier this week said the country is on track to vaccinate more than four million people by the end of September.