The European Union is set to receive 50 million doses of the Sputnik V coronavirus vaccine from Russia in June.
Professor Luke O'Neill said a number of countries in the EU are already using it, and this will increase when it is approved by the European Medicines Agency (EMA).
He told Pat Kenny: "Sputnik is now approved in Slovakia and Hungary, they're using it.
"The EMA is examining Sputnik V - they will report soon on it to see if it's to be approved.
"And the Russians have said they're going to give 50 million doses to the EU as soon as the EMA has approved it.
"It's coming down to which country or companies have the biggest factory, that kind of thing.
"And the Russians are claiming they have no issue with supply - and they can supply their own country and also export it".
Prof O'Neill said the UK's regulatory body, the Medicines and Healthcare products Regulatory Agency (MHRA), could actually approve the Sputnik V vaccine drug ahead of the EMA.
"I suspect they may approve it first, ahead of the EMA, in the usual way.
"The Russians have guaranteed 50 million doses in June, so I think that'll happen by the way.
"I predict the EMA will approve this vaccine, there's no question - cause it is very safe and efficacious - it's like the Johnson & Johnson vaccine [with] very similar technology.
"So why wouldn't the EMA approve it, and the Russians have said we can supply it.
"500,000 doses could be [in Ireland] in June."
Professor Kingston Mills - Professor of Experimental Immunology at Trinity College Dublin - has previously said the data around the vaccine is 'great'.
He said: "[Sputnik] looks great… the efficacy in that Lancet paper showed 92%.
"The EU is not dragging their heels, to be fair. They’re currently doing a rolling review - they’re looking at the data. They haven’t yet had an application for a full market authorisation yet… but they expect to get that soon."
He said that Hungary, Slovakia and Montenegro had "started negotiating directly with the Russians" to regulate the vaccine - and Hungary has already given it emergency use authorisation.
He said: "They’re allowed to do that… but it’s frowned on by the EMA."
It comes as the EMA approved the one-shot Johnson & Johnson vaccine on Thursday.