Taoiseach Micheál Martin said it is "repugnant" that a private hospital used spare jabs to vaccinate teachers from an exclusive school.
Coronavirus vaccine operations at Dublin's Beacon Hospital have been suspended after it used 20 doses, which were left over after a daily vaccination session, to vaccinate some staff members at St Gerard's private school in Bray.
Mr Martin said what happened was "unacceptable".
"I've condemned it. It's repugnant something like that would actually happen," the Fianna Fáil leader said on Monday.
"That's why the administration of vaccines there has been suspended. The vaccines belong to the people of Ireland.
Mr Martin said people have been prioritised to give them the "greatest level of protection", and to reduce illness and reduce death.
"That has worked, broadly speaking, in terms of the rollout of the plan," he added.
"It's been effective and the impact has been quite dramatic and the HSE is overseeing an examination of what happened there.
"There are clear protocols laid down in terms of the prioritisation and the manner in which any surplus vaccines are to be used at the end of that particular vaccinated session."
The south Dublin hospital, which was administering vaccines as part of the state programme, has apologised for its decision, claiming it was made under "time pressure".
The hospital admitted the move was not in line with the HSE's sequencing guidelines.
The Beacon is a beneficiary of state contracts for outsourced medical services.
Meanwhile, Mr Martin remained tight-lipped about any plans to lift Covid-19 restrictions next month.
The Government is expected to make an announcement about plans for restrictions on Tuesday, however, the Taoiseach refused to take questions about it.
He told reporters any announcements or updates would be made on Tuesday.
It comes after public health officials met on Monday to review the easing of coronavirus lockdown measures.
It also comes amid increasing concern over rising Covid-19 cases in the country.
The most severe level of restriction, Level 5, is currently in place until April 5.
The National Public Health Emergency Team held a lengthy meeting on Monday.
Its recommendations are being considered by the Cabinet sub-committee on the pandemic response this evening before a full meeting of Cabinet on Tuesday.
The Taoiseach is to make an announcement following the Cabinet meeting.
Some limited relaxations, potentially in relation to outdoor activities and the 5km limit on travel, are expected.
But it is believed it will be May or June before a greater easing of restrictions will be made.