Tánaiste Leo Varadkar has blamed an undelivered consignment of 25,000 AstraZeneca vaccines for the failure to administer the targetted 100,000 vaccines to the public last week.
Mr Varadkar said the Government only found out that the delivery was not going to arrive at short notice.
He said the Government will examine "options for securing additional vaccines from elsewhere" but added there is a worldwide shortage of doses.
"When it comes to vaccines our targets are based on two things that are not under our control. One is the vaccine being approved by the European Medicines authority....and secondly the vaccines actually arriving from abroad where they're made.
"Things that are under our control are making sure that once the vaccines get in the country we have them in people's arms within a week, and that's happening. Unfortunately, there will be occasions when the delivery doesn't arrive, and there will be weeks where we're behind target or weeks where we're going to catch up and that's what's going to happen with this."
Also during the interview on Virgin Media television, Mr Varadkar laid out the four 'data points' for restrictions being eased on April 5.
- is the vaccine rollout on schedule?
- are there any variants we need to be particularly concerned about?
- are the number of cases every day still falling?
- is the pressure on hospitals being relieved and the numbers in ICU still going down?
"If the answer is yes to those questions, then we will be able to do some reopening on the fifth of April," he said but added the easing will be limited.
"The kind of things that you might see happening on April 5 are potentially construction going back to work. That's a lot of people going back to work which would be very welcome and very important in terms of building houses. Also, the five-kilometre limits being relaxed. I think we are all dying to get out a bit more and get out of this five-kilometre circle that we're all in. Then (there is) also the possibility of more outdoor activities being allowed. It will be outdoor first, and then we look at the situation again about 21 days later so that's April 26."
Mr Varadkar also said he does not believe the UK will be able meet the dates it has set out.
"I would be very surprised if [the UK was] able to meet those dates, quite frankly. One thing we don’t want to do is give people a date we can’t stand over.
Meanwhile, several Fianna Fáil TDs have strongly criticised the pace of the country's vaccination programme.
A number of deputies shared their anger at last night's parliamentary party meeting that many over 85s still don't know when they will get their jab.
Dara Calleary said he had little faith in the HSE to deliver given some experiences while Joe Flaherty said many older people have been left broken hearted.
Co-leader of the Social Democrats, Roisin Shortall, says transparency is needed on the roll-out and the delivery of vaccines into the country.
"At the moment, we have no way of guaging how efficient or otherwise the HSE is in getting the vaccinations out.
"That is why I've called on the Government to provide those figures so that we know what the performance is."
It comes as the health service failed to hit the government's target of administering 100,000 doses last week, with supply issues blamed.
But professor of virology at UCD, Gerald Barry, says Ireland is doing well compared to other EU nations.
"When you compare us to countries like the UK, it appears that we are moving relatively slowly but in comparison to other countries in Europe I think we are doing quite well," said Prof Barry.
"I think we are vaccinating as many people as we get vaccines delivered into the country and that is all we can really do for now.
"There is no doubt the vaccine is going to have a dramatic impact on this whole situation."
Meanwhile, an advisor to the HSE says the falling incidence rate is no reason to drop our guard against Covid-19.
The 14 day rate is currently 199 cases per 100,000 people which is the lowest level since Christmas eve.
566 additional cases were reported alongside 25 patient deaths yesterday evening.
GP Advisor to the HSE Dr Ray Walley says people need to keep following the same rules they have been all along.
"We are always going to have new virus variants happening and the basic way you are going to keep yourself and your family and your nearest and dearest free of this virus is to ensure you wear a mask, keep a social distance, wash your hands.
"If one becomes symptomatic, isolate immediately and contact your GP."