Tánaiste Leo Varadkar has said the Government has not yet called on pharmacists who have signed up to administer COVID-19 vaccines.
But he said they will likely do so in June and July.
Asked about the target to offer a vaccine to over 80% of the population by the end of June, he told The Hard Shoulder: "It is a stretch target, we do believe it's achievable.
"But it does rely on supplies, and then does rely on us continuing to be able to administer vaccines within a week of them arriving into the country".
He said as vaccines continue, "it's really only when we get to that point where we actually have to do 400,000 a week or 500,000 a week that we'll know for sure whether it's possible.
"But there is additional capacity there - 1,200 pharmacists who signed up to carry out vaccines, we haven't had to call on them yet.
"I believe we will in June and July".
On the re-opening plan for the country, he said: "The main reason why we can do this of course is the vaccine programme, and that is accelerating very rapidly at the moment.
"But it's still the case that 70% of people haven't been vaccinated at all, and we are relying on people to really continue to exercise personal responsibility and follow the rules around social distancing, and avoiding large crowds and minimising contacts.
"Notwithstanding the fact that there will be so many new opportunities now to do the opposite".
"One thing we have had useful evidence from, and this is helpful, is that there are countries that are a bit ahead of us in terms of their vaccine programmes.
"The United Kingdom, Israel and the United States - both the UK and Israel are ahead of us in re-opening as well.
"So we have been able to model what's happened there against what might happen here."
'Get out and spend'
On people spending money as they come out of lockdown, Mr Varadkar said this will keep others employed.
He said there is "around" €12bn of savings in Irish banks currently.
"The situation is that before the pandemic, there were roughly 2.3 million people working in Ireland - about 500,000 lost their jobs and our dependent on the Pandemic Unemployment Payment.
"Many more than that - about 1.5, 1.8 million - held on to their jobs, and in many cases like in the multi-national sector, the public sector actually would have seen a pay increase.
"And a lot of people are saving, because they haven't been able to spend in the way they would normally.
"One of the things we can do to get people back to work is actually to spend that money."
And Mr Varadkar said he hoped outdoor events, such as Electric Picnic and the National Ploughing Championships, could take place in September.
"I really hope so - both those events are September."
It followed comments on Lunchtime Live earlier from Anna Marie McHugh from the National Ploughing Championships.
She said: "This whole talk now that [Minister] Catherine Martin has had about the pilot schemes: who is she negotiating with on these pilot schemes? What regulations are being put in place?
"We're the biggest outdoor event in the country, and I've had no conversation at any time with Catherine Martin or any of her team."
She also expressed concerns over whether organisations would be liable if a person attending caught COVID-19.
Mr Varadkar said he would "make sure" somebody from Government makes contact with Ms McHugh.
But he said he does not share insurance concerns around contracting the virus at such events.
"I hear that concern, but I don't share it - COVID is an infectious disease, it's a respiratory virus, it's not a new one."
And he said several other viral infections, which can be caught at large settings, are not the subject of legal proceedings
"You've heard of people taking ages to recover from shingles or glandular fever, and I've never heard of anyone suing the event they attended and being successful.
"I'm not saying it can't happen, but I would really be surprised if that's where we ended up in our courts".