The National Immunisation Advisory Committee has recommended the AstraZeneca vaccine should not be given to people under the age of 60.
It follows concerns the vaccine is linked to cases of very rare blood clots, with a number of EU countries limiting its use.
The recommendation has been made to the government this evening.
It also includes new advice for people who've had their first dose of AstraZeneca.
It says the 12 weeks gap for receiving the second dose should remain for those over 60 and anyone under 60 considered high risk.
However, it says the timeframe should be extended to 16 weeks for those under 60 not considered at high risk, to allow further assessments take place.
Over the next three months, 20 per cent of the vaccines due to arrive in Ireland are from AstraZeneca, which gives some scope to find a workaround that will cause minimal impact to the roll-out timeframes.
More than 233,000 doses of the AstraZeneca covid-19 vaccine have been administered in the Republic so far.