It comes amid growing concern about the spread of the Delta variant in younger age groups.
NPHET is urging people who haven't been vaccinated yet to avoid meeting up indoors this weekend.
Around 10 per cent of close contacts are now testing positive.
HSE National Lead for Testing and Tracing, Niamh O'Beirne, says it's higher in younger age groups:
"Younger people - there are certainly more close contacts in those age groups. And the positivity of close contacts in those age groups is much higher than the norm, so in the 19-24 age group, and the 13-18 age group, the positivity rate is over 15%."
