The lining of children’s noses protects against Covid-19

When compared to adults, children usually experience milder Covid-19 symptoms and are even less susceptible to infection. Until recently though, the factors driving this pediatric resistance to SARS-CoV-2 were largely unknown.

A new study led by the University of Queensland in Australia has found that children’s nasal epithelium (the lining of the nose) inhibits infection and replication of the ancestral strain of the virus that emerged in Wuhan, as well as the Delta variant. Unfortunately, these results were not found in the case of the Omicron variant.

The scientists collected samples of primary nasal epithelium cells (NECs) from 23 healthy children aged 2-11 and 15 healthy adults aged 19-66 from Australia, and exposed them to SARS-CoV-2 in order to assess the infection kinetics and antiviral responses in children compared to adults.

The results revealed that the ancestral strain of the coronavirus replicated less efficiently and was linked to a heightened antiviral response in the nasal epithelial cells of children – features which were also observed with the Delta variant, but not the more recent Omicron one.

 “We have provided the first experimental evidence that the pediatric nasal epithelium may play an important role in reducing the susceptibility of children to SARS-CoV-2,” the study authors wrote. “The data strongly suggest that the nasal epithelium of children is distinct and that it may afford children some level of protection from ancestral SARS-CoV-2.” 

“Importantly, the Delta variant also replicated to significantly lower titers in the NECs of children. This trend was markedly less pronounced in the case of Omicron. It is also striking to note that, at least in terms of viral RNA, Omicron replicated better in pediatric NECs compared to both Delta and the ancestral virus. Taken together, these data show that the nasal epithelium of children supports lower infection and replication of ancestral SARS-CoV-2, although this may be changing as the virus evolves.”

The study – published in the journal PLoS Biology – has several limitations, such as the small sample size. Future clinical studies are needed to validate these preliminary findings in a larger population and to clarify the role of other factors, like antibody levels, in protecting children against Covid-19. Moreover, the fact that children seem less resistant to infection with the highly contagious and immune-evasive Omicron variant suggests the need for careful investigation of how newly emergent variants may impact various age groups.

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By Andrei Ionescu, Earth.com Staff Writer