The Chair of the NPHET Epidemiological Modelling Advisory Group has said that 100 children, aged between five and 14, have tested positive for Covid-19 in Ireland in the last two weeks.
Professor Philip Nolan said that these are "in the context of household outbreaks".
Speaking on RTÉ's This Week programme, he said there will be Covid-19 clusters in schools, but it is likely such cases will have been contracted at home, rather than in schools themselves.
Prof Nolan said it was a very anxious time for parents and teachers, adding that we know a lot more about the virus now than we did in March.
He said he could offer "a great deal of assurance" to people that the virus would not spread from schools back home to vulnerable people.
He said there is very little evidence internationally that schools are a major site of transmission or spread of Covid-19. He said children can get the disease, but they are contracting it more so at home than elsewhere.
"We will see cases in students and cases in teachers and clusters in schools, but when we see that, we need to think carefully and look carefully, because it remains unlikely when we see that," he said.
He added: "If, for instance, there are two children in the same school with Covid in two months' time, it is much more likely that those two kids have separately got it within their own households, rather than transmitting from child to child within the school."
He said Germany was a good example, where cases confirmed in schools stemmed from children contracting the virus in a home setting.
In almost all of those German cases, it was quite certain that the virus was acquired at home, he said.
Prof Nolan said he does not think the dinner event in Galway has particularly hindered NPHET's capacity to relay public health guidance, and echoed Acting Chief Medical Officer Dr Ronan Glynn saying that public anger would not stop the virus from spreading.
He said the core advice was that adults needed to stop congregating in large gatherings. He said such large gatherings were the core concern for NPHET.
If we can only have 6 people in our houses, how can we have 30 children in a classroom? It's a reasonable question. But it’s not a contradiction; in fact, these measures are connected and coherent. The following explanation is a simplification, but illustrates the principle. 1/8 pic.twitter.com/tSrWVyjodf— Professor Philip Nolan (@President_MU) August 21, 2020
He said everyone knows the difference between a crowded setting and a carefully managed classroom. He said people needed to use their common sense in that the virus transmits through sustained close contact.
Prof Nolan said his fundamental appeal was that people needed to avoid crowded settings, as that will quench the virus, and allow people to return to some normality.
Yesterday, an additional 156 cases of Covid-19 and two further deaths were reported to the Department of Health.
There has now been a total of 1,777 coronavirus-related deaths here and 27,908 cases. This includes the denotification of one death and three cases.
Of the cases notified yesterday, 68 are confirmed to be associated with outbreaks or are close contacts of a confirmed case while 15 cases are from community transmission.