The Government's goal of vaccinating 80% of adults by June still stands, the Taoiseach has said, telling the Dail: "The target is still the target."
It comes after the HSE's national director responsible for the vaccine rollout, Damien McCallion, told the Oireachtas Health Committee he is "not in a position" to confirm if the target will be reached.
Issues with supplies have created numerous setbacks for the vaccination programme, with news on Tuesday that a delivery of AstraZeneca jabs this week had fallen from an expected 45,000 to just 9,000.
Labour leader Alan Kelly raised the issue at Leaders' Questions on Wednesday, asking the Taoiseach if there are changes to the vaccine rollout.
Micheal Martin responded: "The target is still the target, I'm not confirming any changes whatsoever."
He highlighted the challenges presented by decisions taken by the European Medicines Agency (EMA) and the National Immunisation Advisory Committee (NIAC) around the safety of the AstraZeneca and Johnson & Johnson vaccines.
The NIAC has advised that the AZ jab should only be given to people over 60, and will meet this week to discuss use of the J&J vaccine after an EMA review over rare blood clotting concerns found the benefits outweigh the risks.
The Taoiseach said: "The key issue, yet to be determined, is the issue of the interval between doses, which has been examined again by NIAC in consultation with the chief medical officer."
AstraZeneca has indicated that its supply capacity could increase significantly if it is given certain authorisations around manufacturing, Mr Martin said.
He added: "Depending on the outcomes of a lot of that, the situation can improve significantly.
"The issue then will be the administration of vaccines in Q2."
Mr Martin did not respond to a question around goals to administer 250,000 vaccinations per week by April - a target Mr McCallion said on Tuesday would not be met.
Mr Kelly said: "For the record, for the public watching, the Taoiseach of Ireland has said at this moment in time there's no change as regards the 82% by June and 250,000 by next week.
"You said there was no change and that is the effect of saying there is no change."
Mr Kelly also suggested that a new vaccine oversight group in the Taoiseach's department had been established because of Health Minister Stephen Donnelly's performance.
Mr Martin responded angrily, saying: "Absolutely not - it's nothing to do with Minister Donnelly's performance.
"'We've just heard the Taoiseach say X or Y.' I'm not interested in that kind of infantile politics or juvenile politics."
Mr Kelly shouted over the Taoiseach: "That's diversion tactics is all it is. Answer the question for the people of Ireland, the people deserve to know."
Mr Martin said: "The group that has been established, that you've asked about, is a group that involves the HSE, that involves NIAC, because there is a relationship between advice and the operationalisation of that advice in terms of the administration of vaccines.
"That to me is a simple, positive thing to do."