It's too early to tell whether vaccinations will stop coronavirus transmission and allow for safe international travel, Professor Sam McConkey says.
However, the infectious disease specialist says a vaccine certificate system could be put in place once that happens.
Yesterday, European Commission President Ursula von der Leyen said the EU will unveil its plans for a travel 'green pass' system later this month.
The digital pass would provide proof a person has been vaccinated against COVID-19, as well as results of tests for those who have yet to receive a vaccine.
Some states such as Greece have pushed hard for a 'vaccination passport' system to allow tourism resume.
However, other countries, such as France and Germany, are reported to be concerned people who haven't been vaccinated yet could be discriminated against under such a system.
Professor McConkey - Infectious Disease Specialist at the Royal College of Surgeons Ireland - told Newstalk Breakfast we still need to see more data about the vaccines.
He said: “We need to find out does it work, is it effective and do the vaccines really prevent transmission well enough to make it safe for people who have been vaccinated to travel from one country to another. We don’t really know that yet.
“To use a simple metaphor, it’s a big like deciding to build a bridge, and you don’t know if it will stay up or not.
“I think we need the data first that this works and then put it in place. It’s not so difficult to put in place quickly because there’s a similar system in place for yellow fever."
Professor McConkey noted that even in highly-vaccinated areas, there's still likely to be 5-10% of people who haven't got the vaccine, as well as people who didn't respond to a vaccine they did get.
He said these groups will often be vulnerable ones - such as elderly people or those on chemotherapy or dialysis - while there are also concerns about more transmissible variants.
He added: “The vaccine data is all very fresh from Israel and Scotland.
"Certainly it seems to protect for three months at least, and I’m optimistic it will be for longer than that - maybe even up to a year. But we really don’t have that data."
'A uniform certificate system'
Fianna Fáil MEP Billy Kelleher agreed that it's important that we get more data on transmission.
However, he believes there's a need to start planning for a digital pass system.
He said: “It clearly is not going to work to have a situation where people will be walking around with bits of paper in their pockets, or PDFs or screenshots showing they have been vaccinated or had a PCR test.
“We do need to put a uniform certificate system in place, so it is inter-operable across all European countries, and possibly even [have] discussions with the UK and America as well.”
Mr Kelleher said he himself has seen 'chaotic' scenes in airports as people produce different types of evidence that they've had a negative PCR test before travelling.
He said: “There is evidence to suggest [the vaccines do] reduce transmissibility, but I’m not an epidemiologist, virologist or medic. I’m just pointing out from a political perspective we should put in place a vaccine certificate programme.
“We should at least embrace it and encourage it, and use it in the event of the science and evidence coming in about reductions in COVID-19 by people who have been vaccinated."
He added that Greece has already done a bilateral deal with Israel to allow vaccinated people to travel, so it's important measures are put in place across the bloc.