More than 220 cases of the Delta variant of Covid-19 have been reported in the Republic, according to latest data.
The vast majority of cases, at 49.3 per cent, were detected in the 19-34 age category, followed by the 34-44 age category, at 19.6 per cent.
Cases were less common in under-18s and in the age cohorts which have received vaccinations, aged over 45.
The most recent data published by the Health Protection Surveillance Centre on Friday relates to samples tested up to mid-June.
The data is incomplete as it takes about two weeks to genetically sequence for the variant involved. The current number of cases reported is also only from a small number of samples sequenced to date.
The Delta variant of Covid-19 is suspected to now account for nearly 70 per cent of new cases of the virus in the State, the National Public Health Emergency Team (Nphet) has said.
Transmissible
Three weeks ago, the highly transmissible strain was linked to just 9 per cent of infections. This increased to 28 per cent the following week, and 55 per cent of cases last week.
A statement from Nphet on Thursday said incidence of the virus was growing at 2 per cent per day in Ireland, and the reproduction number is now estimated to be between one and 1.2.
Meanwhile, cases of the variant have risen almost fourfold in the UK in less than a month, according to Public Health England figures. It continues to account for about 95 per cent of confirmed cases of coronavirus across the UK.