There has been a surge in school outbreaks in the latest figures confirmed by health officials.
The statistics were released by the Health Protection Surveillance Centre (HPSC) on Wednesday morning.
They show that a total of 90 outbreaks were notified in the seven days to last Saturday, resulting in 412 Covid-19 cases.
This is a sharp increase on the 40 outbreaks recorded in the previous week, which led to 191 infections.
An "outbreak" is defined as a cluster of two or more linked Covid-19 cases.
The vast majority of these clusters were in primary schools, accounting for 78, while 11 were in post-primary and one was in special education.
The latest HPSC report also shows that four cases of the Mu variant have been reported in Ireland.
The national incidence rate of the coronavirus is at 390.4 cases per 100,000 population.
As of Monday evening, the worst-affected counties in Ireland by the virus were Monaghan, Donegal, Louth, Carlow, and Laois.
The five counties with the lowest incidence rate for the last 14 days are Galway, Wicklow, Leitrim, Wexford, and Sligo.
It comes after Chief Medical Officer Dr Tony Holohan has urged everyone to get their Covid-19 jab.
Speaking on Tuesday, Dr Holohan said: "Covid-19 vaccines are providing very effective protection from severe illness and have fundamentally changed the risk profile of Covid-19 in Ireland - it is important that all of us receive our Covid-19 vaccine as soon as it is available to us.
"Once again today, we see more elements of our society and economy reopen. If you are fully protected through vaccination, then you can have confidence that your vaccination, and your continued adherence to the public health advice appropriate to each environment, is the best way you can protect yourself from Covid-19.
"If you display cold or flu-like symptoms like cough, fever, headache, sore throat and blocked or runny nose, self-isolate immediately.
"Please do not meet up with others or attend events, work or school. Arrange a PCR test through the HSE as soon as possible."
