The highest incidence rates of Covid-19 in kids were recorded when kids were on holidays from schools, a HSE briefing has heard.
There were on average 1,000 cases per week among zero to 18-year-olds before the summer break this year.
However, this figure rose to between 3,500 and 4,000 a week when children were out of school.
Dr Abbey Collins, a HSE public health specialist, said this was a reflection of stringent test and trace protocols and strict mitigation measures implemented across the board in school settings.
She said: "We saw the largest number of children get Covid over January.... over July and August, when the children haven't been in school.
"There is an element about stability of life and being in an environment where there is a quite sort of strict, in the nicest possible way, enforcement of the mitigation measures that we are asking our schools. That is having an impact."
Outside of schools, children often only get tested for the virus if a parent or family member has tested positive, Dr Collins said.
In schools, however, proactive testing and tracing is done where any positive case arises.
"We go into the school and we proactively test a large number of people," she said.
"I think it's just interesting that there were 1000 cases per week on average throughout the school term.
"And just before we returned after the summer holidays there were 4000 cases a week in zero to 18-year-olds.
"So clearly you're more likely to get Covid in the school holidays if you go by those numbers.
"I think that's the importance of mitigation measures across the board, rather than just in one setting."
The Health Information and Quality Authority (HIQA) has completed a review on mask-wearing for children in primary schools, which is to be considered by Nphet at a meeting next week.
Dr Collins said there are "a lot of complications" associated with compulsory mask wearing for children.
She cited the fact that in the US, about 30% of children wear glasses, which can cause problems for mask wearing.
"Small ears and glasses and face coverings and steaming up and trying to see and eat and drink, ends up requiring assistance for those face coverings," she explained.
"And that means someone getting very close to assist someone putting on their face covering.
"Those are the kinds of things that get balanced in those discussions."
Dr Colm Henry, the HSE's chief clinical officer, said there is "a lot for us to be optimistic about now."
It comes as 1,292 further cases of Covid-19 were confirmed in Ireland this evening by the National Public Health Emergency Team (NPHET).
The Department of Health says there are now 331 people in hospital, with 54 of those in ICU.
"The average numbers of cases per day, the five-day moving average, it's 1400, 1500 per day. It's beginning to fall now," Dr Henry said.
"It's dropped 14% compared to last week, about 20%, compared to the figures two weeks ago."
"Equally significantly, some of those age groups that were causing concern to us, notably the 18 to 24 years group for example, we were quite worried about them, as they were principal drivers of infection, not just in their own group age group but elsewhere.
"We're seeing a drop of 20% in the incidence of disease among this age group."
