One in 20 pupils identified as being a contact of a positive coronavirus case in school went on to contract the virus within 14 days, a new report from Public Health Scotland shows.

The research, which focuses on the 2020-21 school year and is published today, shows that 5.2 per cent of pupils identified as contacts of a positive case in school subsequently tested positive for Covid-19 within 14 days of exposure.

A higher proportion of primary school pupils identified as having contact with a positive case went on to develop Covid (7.9 per cent) than secondary students (2.3 per cent).

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Researchers believe that could be because primary school pupils had more in-person education than those in secondary. They also point out that mitigations differ - for example, secondary students are required to wear masks in school.

However, they ultimately conclude that “it is not possible to provide a definitive interpretation for the differences”.

Research into how Covid has spread in schools

The research is timely given heightened concern about school safety as a result of the recent surge in Covid cases in Scotland, as well as changes to the rules on self-isolation which mean that now even pupils who have sat next to a positive case in class will not necessarily be told to stay home until tested.

However, while the Public Health Scotland report might offer some reassurance because it shows that a low proportion of pupil contacts in the same school year went on to develop Covid-19, it also finds that “notable differences were observed in term 3”, when 10.5 per cent of primary pupil contacts went on to develop Covid, and 3.5 per cent of secondary studeht contacts tested positive.

The report puts the rising proportion of contacts who went on to become Covid cases themselves in the summer term down to “the emergence of the Alpha and Delta variants”.

Today, first minister Nicola Sturgeon told the Scottish Parliament that “the Delta variant is significantly more transmissible than previous strains”.

She said: “Just as vaccines have changed the game for us in a very good way, Delta has changed it in a very challenging way.”

The Public Health Scotland research looked at pupils aged 4 to 17 who had received a positive PCR test and for whom 10 or more contacts had been identified in the same year group, in the same school, because “these criteria were most likely to represent contact tracing of a class”.

In total, there were 1,503 positive cases that fit the criteria and these positive cases had led to 30,886 pupils being identified as contacts.

In over half of the positive cases (61.9 per cent), none of the pupils identified as contacts tested positive for Covid-19 within two weeks of exposure. In 17.1 per cent of the positive cases, there was one further case among the contacts and, in 21 per cent of the positive cases there were two or more further cases.

The report says: “Overall, this report shows that a low percentage of school-year pupil contacts subsequently become Covid-19 cases themselves, but that this proportion increased over the school year in the context of the emergence of the Alpha and Delta variants and was higher in primary schools than in secondary schools.”