An immunology professor says it's inevitable border counties will start to see an increase in the Delta variant.
The strain accounts for 25 per cent of Covid-19 cases in the North.
The chief medical officers on both sides of the border have appealed to the public to avoid activities which could put them at risk of contracting the virus.
Professor Kingston Mills of Trinity College Dublin says the spread of the Delta variant is dependent on what travel restrictions are put in place.
Prof Mills said: “I can't see any way, if the Delta variant becomes the dominant variant in Northern Ireland, that we're going to stop it becoming the dominant variant in the border counties unless we put in place extremely stringent travel measures not only with mainland UK but also with the North.”
In an interview with BreakingNews.ie, University College Cork Professor Ivan Perry said: “I would say it’s highly likely, it would be borderline miraculous if it doesn’t become the dominant strain because the patterns of this virus operates on haven’t changed.
“You can see why the British government made the decision even though they were very keen on their day of freedom, I see that as a red flag for us particularly as our rate of vaccinations is a good bit lower than the UK.
“We have to proceed with caution if we want to protect our outdoor summer and have a reasonable change of things getting back to near normal in the autumn.”