Children are protected from severe COVID-19 because their innate immune system attacks the virus quickly, new research has shown.
The research, led by the Murdoch Children ‘s Research Institute (MCRI) and published in Nature Communications, found that specialized cells of the child’s immune system rapidly target the new coronavirus (SARS-CoV-2).
MCRI doctor Melanie Neeland said the reasons why children have mild COVID-19 disease compared to adults, as well as the immune mechanisms that support this protection, are unknown until this study.
“Children are less likely to be infected with the virus, and up to a third are asymptomatic, which is strikingly different from the higher prevalence and severity seen in children for most other respiratory viruses,” she said.
“Understanding the basic age differences in the severity of COVID-19 will provide important insights and opportunities for prevention and treatment, both for COVID-19 and for possible future pandemics.”
The study included the analysis of blood samples from 48 children and 70 adults in 28 households in Melbourne infected or exposed to the new coronavirus. Immune responses were monitored during the acute phase of the infection and for up to two months thereafter.
Francesca Orsini and Alessandro Bartesaghi participated in the study along with their two daughters, Beatrice and Camilla, after they had COVID-19 on a positive test.
Both daughters, aged six and two, had only a mild runny nose, but Francesca and Alessandro had extreme fatigue, headaches, muscle aches, and loss of appetite and sense of taste. It took Francesca and Alessandro at least two weeks to fully recover.
Dr Neeland said the study showed that children with COVID-19 had a stronger innate immune response to the virus than adults.
“Coronavirus infection in children was characterized by activation of neutrophils, specialized white blood cells that help heal damaged tissues and resolve infections, and reduce immune cells that first respond, such as monocytes, dendritic cells and natural killer cells from the blood,” she said. “This suggests that these immune cells fighting the infection migrate to the sites of infection, quickly removing the virus before it has a chance to really catch it.”
“This shows that the innate immune system, our first line of defense against germs, is crucial in preventing severe COVID-19 in children. Importantly, this immune response did not replicate in the adults in the study.”
But dr. Neeland said children and adults who were exposed but who were negative for coronavirus also changed their immune response.
“Both children and adults increased the number of neutrophils, seven weeks after exposure to the virus, which could provide a level of protection against the disease,” she said.
The study confirms previous MCRI research that found that three children in a family in Melbourne developed a similar immune response after prolonged exposure to the coronavirus from their parents.
Research has shown that children were infected with the coronavirus, but were able to establish an immune response that was very effective in stopping the virus from replicating, meaning they never returned a positive test.
Researchers from the University of Melbourne and the Royal Children’s Hospital also contributed to the study.
Publication: Melanie R. Neeland, Samantha Bannister, Vanessa Clifford, Kate Dohle, Kim Mulholland, Philip Sutton, Nigel Curtis, Andrew C. Steer, David P. Burgner, Nigel W. Crawford, Shidan Tosif and Richard Saffery. ‘Congenital cell profiles during the acute and convalescent phase of SARS-CoV-2 infection in children,’ Nature Communications. DOI: 10.1038 / s41467-021-21414-x
Available for interview:
Dr. Melanie Neeland
Dr. Shidan Tosif
Professor Richard Saffery, leader of the MCRI Group, Infection and Immunity
Francesca Orsini and Alessandro Bartesaghi, the family involved in the study
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