Two family members of staff at the Rotunda Hospital received Covid-19 vaccines which it says would have been wasted otherwise.
It comes after a similar controversy at the Coombe Hospital, where 16 family members of staff at the maternity hospital received the coronavirus vaccine.
A total of 37 people received the vaccine from remnants of vials delivered to the Rotunda Hospital in Dublin which were intended for its staff.
In a statement on Monday, the Rotunda Hospital said it received 93 vials of the Pfizer/BioNTech vaccine on Wednesday, January 6.
Each vial contains six doses, and the statement said "every one of these six doses were administered to staff working at the Rotunda".
However, excess doses of the vaccine left in the vials were subsequently administered to the community.
The statement said: "These remnants would have expired within a number of hours, if not used, and would have been discarded.
"Rather than wasting any vaccine whatsoever, and following immediate discussion with leadership at the National Immunisation Advisory Committee (NIAC), the Rotunda requested expressions of interest from the local community, who could attend the hospital within an hour, prior to expiry of these vaccines, and who would be willing to accept these unapproved vaccine remnants.
"Thirty-seven people, including local GPs and members of other vulnerable groups, agreed to attend and to avail of the non-approved vaccine remnants.
"The Rotunda is of the view, and is supported by NIAC, that this was the morally correct thing to do and a wholly appropriate response in the setting of a pandemic, such that no vaccine was wasted and the maximum good was achieved."
It is understood that two family members of staff at the hospital were among those in the vulnerable groups who received the excess doses.
The statement added: "It must be noted that even if Rotunda staff could attend at short notice to receive the vaccine remnants, the hospital was not approved to administer it to them.
"Equally, the 37 non-Rotunda personnel who received the vaccines did so in the full knowledge they were receiving a non-approved vaccine remnant."
Earlier on Monday, the health minister asked bosses at the Coombe hospital in Dublin for a "full account", after it emerged that Covid-19 vaccinations were given to family members of staff.
The relatives of employees at the south Dublin hospital were vaccinated with doses left over from a batch.
Stephen Donnelly said he will speak to the chairman of the Coombe Hospital board about the matter.
A spokeswoman for the hospital said 16 doses of the vaccine were left after 1,100 frontline workers, including GPs and community health staff, were vaccinated.
The hospital said that of the 16 recipients, nine were over 70 and the other seven were of varying ages.
The hospital said the doses would have been thrown out if they had not been administered.
In a statement on Monday morning, Mr Donnelly said: "I was made aware on Sunday night of a situation with regard to the administration of vaccines on Friday January 8, at the Coombe Women and Infants University Hospital in Dublin.
"Trust in the vaccine programme is of critical importance and what happened should not have happened.
"Our vaccine allocation strategy clearly sets out a priority list for vaccination - and that's currently for frontline healthcare workers and residents and staff of our long-term residential care facilities.
"It does not include family members of healthcare workers.
"I will be speaking with the chair of the Coombe Hospital Board for a full account."
Minister for Further and Higher Education Simon Harris said he was "very concerned" at what happened at the Coombe hospital.
Speaking at Government Buildings on Monday, Mr Harris said he found it hard to understand that there were spare vaccines.
"I have been reading different schools of thought on this during the day and I think some of them are little bit disingenuous," he added.
"There is one school of thought saying 'you shouldn't have wasted the vaccine, you shouldn't be throwing them in the bin' - no-one in their right mind is suggesting to throw them in the bin or waste them.
"What there should be - and there is - is a very clear clinical prioritisation about who gets the vaccine.
"It's very clear that the people who should be getting vaccines right now are people working on the front line with other healthcare staff, and people in nursing homes.
"I am concerned that today in Ireland, there are some frontline workers who haven't yet been able to get the vaccine.
"The idea that we have spare vaccines, albeit just 16 in this case, is a concept I find hard to understand.
"There aren't spare vaccines in Ireland.
"Either there is a situation in place where there is a protocol for spare vaccines and that wasn't followed, or more concerning, if there isn't a protocol in place as to what you do if there are so-called spare vaccines.
"The facts are really important as we need people to have absolute confidence in our vaccination programme."
The master of the Coombe hospital, Professor Michael O'Connell, said the decision was made to ensure that not a "single reconstituted vaccine was wasted".
He added: "Had they not been used, they would have been discarded.
"I was keenly aware of that and, throughout the evening and from 9.30pm onward, I personally made every effort to prioritise and identify additional frontline workers and followed all measures available to me at the time.
"In hindsight, as master, I deeply regret that family members of employees were vaccinated and for that I wholeheartedly apologise."
It came as some 1,800 GPs, practice nurses and other healthcare staff received Moderna jabs at mass vaccination centres in Dublin, Galway and Portlaoise.