Finance Minister Paschal Donohoe has said the Government is determined to try and get as much vaccine for Ireland as it can.
He was speaking after the European Union gave the go-ahead to Johnson & Johnson's one-shot coronavirus drug.
However Health Minister Stephen Donnelly has said the vaccine will not be arriving in Ireland until "late April".
Ireland has an Advance Purchase Agreement for 600,000 doses between April and June.
While Taoiseach Micheál Martin is planning to make contact with AstraZeneca due to its under-delivery.
Minister Donohoe told Pat Kenny Ireland is doing its best, and denied the Government is being 'too polite' to the pharamcitual firms.
"The fact that we've 18 million doses of COVID-19 vaccines ordered for our country just shows how determined we are."
Using an analogy of ordering trainers online that never arrived, he said: "You've ordered trainers, but every other country in the world has ordered trainers as well.
"And of course we're not talking about trainers, we are talking about a vaccine that stops people dying.
"And every single country in the world is trying to get as much vaccine as it can.
"So far from this being a question of politeness or not, we've been determined to try get as much vaccine for our country as we can."
But he said there are no spare vaccines to be relied upon.
"The reality of it is there is no spare vaccines anywhere in the world.
"What we need to do is make sure that AstraZeneca and other manufacturers live up to the commitments that we have.
"And doing this through the European Union is the most effective way of Ireland doing it.
"The EU overall is a customer that is global in scale because of how much vaccine its ordered."
Tánaiste Leo Varadkar has previously said Ireland would be happy to buy extra vaccines from the UK, if they were available.
"We are happy to talk to anybody who has vaccines available but the UK does not have at the moment have a surplus," he said last month.
"They have still only vaccinated about one quarter of their population, way more than us, but still only a quarter.
"I think by the time they have a surplus we will have one too. We have 18 million doses ordered. We will have enough vaccines to vaccinate the entire population twice over."
