About one in 20 school pupils who came into contact with a child who had Covid-19 went on to test positive themselves, according to new research.
Public Health Scotland found that 25,507 school pupils received a positive test for the virus in 2020-21.
Of those, researchers studied 1,503 who had been in contact with at least 10 of their fellow pupils.
A low percentage then contracted the virus, but it increased as the Alpha and Delta variants emerged.
At the same time, Scotland’s testing policy changed which may have led to improved identification of asymptomatic cases.
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The data showed 5.2% of pupils went on to develop Covid-19 in the two weeks after coming into contact with a schoolmate with the virus.
The figure was higher in primary schools (7.9%) than in secondaries, where 2.3% of contacts developed the virus.
Transmission rates were higher between contacts in primary schools
Researchers believe that could be because primary school pupils spent more time in in-person education, than those in secondary.
Other findings documented in the PHS report include:
The percentage of school contacts who tested positive within 14 days of exposure was 1.3% during the autumn term.
It rose to 7.4% in the summer term, as new variants became established in the community.
In 62% of Covid cases with 10 or more contacts, there was no pupil-to-pupil transmission in the same school year.
There was one further case among school-year pupil contacts in 17% of cases, and in 21% there were two or more.
The report said it was not possible to say the transmission happened within schools as the pupils may have been together in other settings.
Education Secretary Shirley-Anne Somerville said the data was “encouraging” but “we must remain vigilant”.
“We will consider this evidence as we keep the approach to contact tracing and isolation policy amongst school pupils under ongoing review as this term progresses to ensure it is proportionate,” she added.