CHILDREN may be protecting their parents against Covid-19, according to scientists involved in a "potentially interesting" study, which may inform decisions to close nurseries and schools in the future. 

Scotland-wide data involving hundreds of thousands of NHS workers found adults living with children aged up to 11 were at no greater risk of testing positive for Covid-19 even during periods when schools re-opened and there was active transmission in the community.

Research led by the University of Glasgow and Public Health Scotland also suggests the risk of testing positive is actually lower for those adults living in a household with a child than it was for those in households without children.

The risk was lower still for adults who lived in households with two or more children under 11 years-old.

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Using Scotland-wide data of 160,000 NHS Scotland healthcare workers aged 18-65 and 250,000 household contacts between March and October 2020, the research team investigated what impact sharing a household with young children had on Covid-positive tests, hospitalisation or death.

It is known that young children are much less likely to have a severe Covid-19 infection, with most having mild or no symptoms at all.

Scientists do not yet fully understand why this happens, although it is thought that children may have increased innate  immune responsiveness following vaccinations and high exposure to respiratory viruses.

Pre-exposure to antigenically-similar infections may also be relevant. Children have higher levels of exposure to endemic coronaviruses than adults, which may enhance cross-protective immunity when they transfer those to parents.

Over the study period - March 1 to October 12 - researchers found no evidence that living with young children increased adults’ risk of Covid, including during the period after schools re-opened. 

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The risk of hospitalisation was progressively reduced with increasing numbers of household children.

The researchers believe that these findings provide evidence of a potentially interesting protective effect against Covid-19 infection in households with young children – an area they now believe warrants further study.

Dr David McAllister of the University of Glasgow, lead author of the study, said: "Our study highlights that more research is needed to understand if young children are conferring some protection to those around them.”

“Any protective effect of children on Covid-19 rate and severity in their household contacts would seem likely to involve cross-reactive immunity to endemic coronavirus infections acquired outside the home – for instance at nursery or school.

"Evidence of similarity between N proteins of SARS-CoV-2 and those of endemic beta coronaviruses (strains Cov-OC43 and Cov-NL63) have now been shown in research studies, and there is also evidence of cross-reactivity in antibody-mediated immunity, although it is currently uncertain how well this protects against Covid-19.

Between  August 12 and October 12, when the schools re-opened, there were an additional 1,337 cases of Covid acros Scotland and 20 cases requiring hospitalisation among adults involved in the study.

Further analysis revealed stronger inverse associations for adults living with pre-school children, compared to those living with primary school children, adolescents, or other adults.

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Compared to adults living with no young children, those living with children were on average 5 years younger, were less likely to live in the most deprived areas and were slightly more likely to be tested for Covid-19.

Dr Rachael Wood Clinical lead for Maternal and Child Health at Public Health Scotland, and an author of the study, said: "This study adds to existing evidence on the limited role that children play in the transmission of Covid-19. 

"More work is needed to explore the idea that living with children might offer adults some protection from infection, but what we can already safely say is that children are not major drivers of Covid-19 transmission."

The study authors said it would be beneficial to investigate if any potential protective effect remains in response to the emergence of new strains of the virus.

The paper, ‘Living with Children and Adults’ Risk of COVID-19: Observational Study’ is published in Archives of Disease in Childhood.