Coronavirus: School reopening 'may have led' to rise in Covid cases in adults

Children are known to be superspreaders of respiratory viruses such as influenza and the common cold, with adults who live with young children in particular experiencing more frequent infections.

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However, the role of children in transmitting the coronavirus which causes Covid "is uncertain", say the authors, although there is good evidence that they appear less likely to catch it in the first place and much less likely to become ill.

The analysis, led by researchers at the London School of Hygiene and Tropical Medicine and Oxford University, drew on GP records for 12 million adults in England.

They evaluated rates of infection, hospitalisation, intensive care admission, and death for two time periods: February to the end of August (wave one) and September to December 19 (wave two).

For adults aged 65 and under, during wave one, living with children of any age "was not associated with an increased risk" of Covid infections or illness compared to adults in a household without children.

Children were classed in two groups: those aged 11 and under, and those aged 12 to 18.

However, the researchers did detect an "increased risk" of infection and Covid-related hospitalisation - but not intensive care admission or death - in adults living with children of any age during the second wave.

Overall, the average number of cases being detected in Scotland each day has been rising since around March 5

The authors write: "These increased risks during wave two were observed at a time when schools remained open, raising the possibility that widespread school attendance may have led to increased risks to households, but other differences between households with and without children could also have explained these observational findings.

"Close monitoring and evaluation as schools re-open will be crucial to inform ongoing policy."

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They note that "the role of schools in transmission of SARS-CoV-2 and the effect of school closures on its prevalence remain uncertain".

The findings of an increased risk during wave two "may have been partly driven by indirect effects—for example, school opening may have allowed parents to travel to work outside the home, increasing potential contacts".

In England, unlike Scotland, workers were encouraged to return to the office from the end of the summer instead of continuing to work from home.

Adults with children also tend to have more interactions, such as for childcare or shopping more frequently.

The authors note that their analysis is not adjusted for different occupational risk among adults, and does not take into account the number of children living in a household.

"We acknowledge that risk may vary by the number of children," they write.

"However, we did not detect strong evidence of higher risk for adults living with increasing numbers of younger children."

The researchers caution that while an increased risk was detected, it was comparatively small.

They estimate that the infection rate for adults living with children aged up to 11 was 850-870 per 10,000, compared to a baseline of 810 per 10,000 (for adults living without children).

For adults living with children aged 12-18 during the second wave, the rate rose to 970-1000 per 10,000 - 20-23 per cent above the baseline rate.

READ MORE: Pandemic has 'exposed and exacerbated' Scotland's health inequalities

For Covid-related hospitalisations, the baseline rate was 160 per 10,000 for adults living without children, but rose to 161-165 per 10,000 for those living with younger children and 162-166 for those living with children aged 12-18 years old - an increase in risk of up to 3.8%.

The findings are in line with previous evidence that teenagers are more likely than younger children to become infected and spread the virus, leading to tougher public health measures in secondary schools.

In terms of a risk to grandparents, the researchers also examined GP records for adults over 65.

The number of children aged 2-19 in Scotland testing positive for Covid has climbed 42% since schools reopened from 605 in the week ending February 14 to 860 in the week ending March 14

Again, they "found no evidence of an association" of an increased risk of infection or illness during wave one among over-65s who shared a household with children of any age.

During the second wave, however, living with children of any age "was associated with an increased risk" of infection, Covid-related intensive care admission, and death.

However, this was based on a comparatively small sample size as only 3% of over 65s in the study lived with children or teenagers.

The timescale for the study predates the rise of the more transmissible 'Kent' variant, which now accounts for around nine in 10 infections in the UK.

In Scotland, schools began reopening to the youngest primary school year groups from February 22, with P4-P7 returning from March 15 along with a phased return for secondary school pupils which sees them split time between classrooms and home learning.

Experts have repeatedly stressed that the risk from the virus has to be balanced against the damage done by missing school.

The authors of the BMJ study write: "Policy decisions around schools must take into account the potential harms associated with school closures, such as adverse mental health consequences and worsening inequalities."