Covid-19 is an endemic among unvaccinated people under 30, according to an immunovirology professor.
The Department of Health reported 1,758 new cases of the virus yesterday.
The number of people in hospital with the virus has risen by 19 to 248, with 48 people in ICU.
UCC's Professor Liam Fanning says social mixing is also contributing to high case numbers.
"Most of those attending hospital are the unvaccinated population.
"This infection is largely now endemic in the unvaccinated population, and the large numbers we're seeing as a result of social mixing of age groups under 30 predominantly, not solely but predominantly.
"That's where the large numbers are coming from."
