Popular hotspots for Irish holidaymakers including France, Italy, Spain and Portugal, would not qualify at this stage for inclusion in the "green list" for a summer getaway due to their higher levels of Covid-19.
The most likely countries to make it to the list are Greece, Slovenia, Finland, Latvia, Cyprus, Estonia, Hungary and Lithuania.
It follows the Government's decision to open up "air bridges" from July 9 with other European countries where rates of the coronavirus are low, and allow tourists from both countries freedom from a 14-day quarantine, including when they return home.
Chief medical officer Dr Tony Holohan said several countries that are holiday favourites would not make it on to the list if the decision was made today because of the 14-day incidence of the virus there.
He also said the list of destinations would not be drawn up until nearer July 9 because of the dynamic situation involving outbreaks which can change the country's rate of virus in days.
"This is a dynamic and changing situation and for anyone making holiday plans, a week or two weeks makes a big difference in the transmission of this virus," he said.
It means that people here trying to book a holiday abroad will be left with little time to book if they want to get a good deal on their break.
To make the list, other countries will need an incidence of Covid-19 similar or lower to here and it must also be reducing. The figures must also be verifiable, he added.
Dr Holohan made it clear that the Government's decision to allow air corridors - which heightens the risk of the virus being imported here from abroad - was a major concern.
Asked about his reaction to more air travel, he added that he was "beyond nervous".
Many of those who will holiday abroad are also in younger age groups and these are a concern due to the number of new cases of the virus emerging among that group over here.
People are still being urged not to undertake non-essential travel abroad, with the risk of infection not only in the holiday destination but also in airports, Dr Holohan added.
The preference was for people to holiday at home, something he himself intends to do, he added.
He was speaking as three more deaths from the virus were announced, bringing the toll to 1,730.
A further 11 new cases were diagnosed, bringing a total of 25,414 so far. Ireland's recent success in driving down the virus has been among the most impressive in the EU.
Professor Philip Nolan of Maynooth University, whose team is tracking the spread of the virus, said all indicators were either stable or continuing to decline, with an average of nine confirmed cases a day in the week to last Wednesday.