The Irish Medical Organisation (IMO) has said in excess of four million vaccines could be available to the Irish population in the next quarter of this year.
It comes as the National Immunisation Advisory Committee (NIAC) is expected to recommend the use of the Johnson & Johnson vaccine for those aged 50 and older.
However, where an alternative vaccine is not available for younger age groups it can be used.
Dr Denis McCauley is chairman of the GP committee of the IMO. He told Newstalk Breakfast this will mean a big increase in vaccine supply.
"The primary good news is that there will be more vaccines available to give to the Irish population generally.
"There was approximately 600,000 vaccines available to give in the next quarter, that was the plan.
"The age groups that it's being allow to use will be 50 to 69 really - that means that that supply could be used."
600,000 Johnson & Johnson vaccines
Dr McCauley said he believes this age cohort "would easily be able to absorb this."
"Taking into account there's been a bit of a supply issue with AstraZeneca - it means that whole amount of Johnson & Johnson, which is 600,000, can now be used.
"So in the rollout the plan was that we're supposed to have 3.9 million vaccines, and there's now an additional 500,000 Pfizer as well.
"Basically, there could be an excess of four million vaccines available in the next quarter to be given to the Irish population - which is the primary thing really".
Dr McCauley said while qualifications for vaccine cohorts can change, the benefits remain.
"I think the benefit of Johnson & Johnson vaccine is... it's a one-dose vaccine which helps, particularly in very at-risk groups - such as people who are homeless and so forth.
"I think it allows it to be given in a more general way: that qualification allows you to say 'We'll give it to the over-50s, but there will be a subgroup of people who you feel cannot be confident that they'll come back for their second dose'.
"Therefore we can use it in those groups also.
"These are really safe vaccines - but the NIAC will generally go for a very safe approach.
"It means that the population that they're giving to, they really think that there's essentially a very, very small risk - less than one in a million - of any issues".
And Dr McCauley added that the Johnson & Johnson decision would keep Ireland on track to have one dose offered to over 80% of the population by the end of June.
"In theory, the supply of vaccine is there to give to the population now - it's just a matter to ensure that the infrastructure and the person on the ground can actually do it, and I think they can", he said.
