Schools remain a “low-risk environment” and children can safely return to the classroom, the chair of the Nphet epidemiological modelling advisory group has said.
Prof Philip Nolan said Nphet has examined the data relating to Covid-19 infection in schools in advance of a full return to all schools on Monday after the Easter break.
The data shows a “moderate and transient increase” in cases of Covid-19 after a return to school, but this can be attributed to increased detection related to an increase in testing.
During a surge, incidence in children is generally lower than the population average, but towards the end of the surge it converges with the population average.
There have been two recent increases in incidence in children, in early-February and mid-March, explained Prof Nolan.
During a surge, incidences rise in 19 to 24-year-olds at the beginning followed by adults between 25 and 64, then teenagers and later in children which slowly converges on the population average towards the end of the surge.
The first increase in children occurred in early February, just after the Department of Health resumed testing of asymptomatic close contacts, which had been paused for most of January.
Children are more likely to be asymptomatic and the number of asymptomatic infections detected in children dropped sharply in January and the resumption of close contact testing led to an apparent increase in incidence in February.
The second increase occurred in mid-March after the first phase of school reopening. It was associated with a very high level of referral for testing, as parents, schools and doctors were vigilant, seeking to protect schools by detecting any infections in children.
Prof Nolan said testing in children increased five to 10 fold, yet the increase in detected infections was much smaller (between 40 and 50 per cent).
Prof Nolan tweeted: “This is reinforced by two observations. The second phase of school reopening, from 15 March, involved a similar number of students (over 300,000), yet was not followed by any detectable increase in incidence.
“Incidence started to drop as soon as schools closed for Easter on March 26th. If transmission were occurring in schools, infections occurring in the last week of term would be detected 5-10 days later, during the break.
“The decrease in the number of cases detected during the Easter break is more likely to be due to an immediate drop in the number of referrals of children for testing, as the level of concern (and vigilance) decreases when schools are closed.
“We note also that school opening is associated with an increase in attendance at workplaces; this increase in social mixing amongst adults carries a risk of increased viral transmission between households.”
Prof Nolan said there is no evidence that the opening of schools leads to an increase in infections in young adults. “There is no population-level signal that this has occurred, with no clear trend in incidence in adults.”
He said children can return safely to school with mitigation measures, providing other contacts are reduced and symptomatic children are kept out of school.
