Low rate of Covid infection among children and teachers after returning to school

Only 4.1% of school close contacts with infected individuals also tested positive for Covid-19, according to researchers from the HSE South’s Department of Public Health at St Finbarr’s Hospital in Cork.

The number of schoolchildren and teachers infected with Covid-19 in the first six weeks of the current school year was low and did not contribute substantially to overall infection rates, a study of schools in Cork and Kerry has found.

Only 4.1% of school close contacts with infected individuals also tested positive for Covid-19, according to researchers from the HSE South’s Department of Public Health at St Finbarr’s Hospital in Cork.

 However, the study said the transmission rate decreased to 2.5% if a high number of cases resulting from a single outbreak in one special school was excluded.

It said the findings were consistent with other studies which demonstrated the opening and closure of schools had little effect on the incidence of Covid-19.

The study found 50 index cases of pupils and 12 teaching staff attending schools in Cork and Kerry infected with Covid-19 in the first six weeks after schools reopened last September as well as identifying 485 close contacts, of which approximately three-quarters were other pupils.

Official figures show over 134,500 pupils are enrolled in primary, post-primary and special schools in the two counties.

Only 20 of the 485 close contacts in school tested positive for Covid-19, of which 11 related to the single outbreak in a special school.

Staff positivity rate

However, the positivity rate among staff close contacts at 6.9% was more than double the rate among student close contacts at 3.1%.

The study found the 20 positive close contact cases arose from a total of 152 infectious school days which amounted to an average of one case per 7.6 infectious school days.

The study examined children and teachers attending primary, post-primary and special schools who were identified with Covid-19 and their close contacts in the first six weeks after schools reopened last September.

Data was collected on index cases and close contacts during their infectious periods of ten days after onset of symptoms or confirmation of a positive test.

Close contacts were classified as people who were within one metre of an infected student or teacher while wearing a mask, or within two metres if unmasked, for a cumulative period of at least 15 minutes over a 24-hour period in either an indoor or outdoor setting.

Overall, children of school-going age accounted for 199 out of 1,614 infected cases in Cork and Kerry over the relevant period.

The study said its results showed schools were only directly responsible for 1.2% of all Covid-19 cases in the region during the six weeks and 2.2% of cases when indirect but related cases were included.

Questions over transmission

One of the report’s main authors, Philippa White, a specialist registrar in public health medicine, admitted the role that schools play in the overall transmission of Covid-19 was not yet fully understood.

However, Dr White added: “The findings of this study demonstrate that the vast majority of close contacts identified in schools had ‘not detected’ test results for Covid-19.” 

She claimed the results were consistent with other studies which have shown a low transmission rate in educational settings.

Dr White said the finding that index cases spent on average 7.6 infectious days in school before a further case emerged was “somewhat surprising.” The report said its findings about close contacts being infected in school could be asserted with a high degree of confidence as there was no other apparent infection source due to a low rate of community transmission of Covid-19 at the time.