THURSDAY, Feb. 18, 2021 (HealthDay News) -- Children have largely been spared severe COVID-19 infection, and new research hints at why.
In the study, children's immune systems attacked the new coronavirus faster and more aggressively than adults' immune systems did, the findings showed.
The researchers analyzed blood samples from 48 children and 70 adults who lived in 28 households in Melbourne, Australia, and who were infected with, or exposed to, the coronavirus. The participants' immune responses were assessed during the acute phase of infection and for up to two months after that.
Children had a stronger immune response to the virus than adults, according to the report published online Feb. 17 in the journal Nature Communications.
"Coronavirus infection in children was characterized by activation of neutrophils, the specialized white blood cell that helps heal damaged tissues and resolves infections, and a reduction in first-responder immune cells such as monocytes, dendritic cells and natural killer cells from the blood," said study author Melanie Neeland, of the Murdoch Children's Research Institute.
"This suggests these infection-fighting immune cells are migrating to infection sites, quickly clearing the virus before it has a chance to really take hold," she said in an institute news release.
The findings showed that "the innate immune system, our first line of defense against germs, is crucial to prevent severe COVID-19 in children. Importantly, this immune reaction was not replicated among adults in the study," Neeland said.
The researchers also found that children and adults who were exposed to, but tested negative for, the coronavirus also had altered immune responses.
"Both kids and adults had increased neutrophil numbers, out to seven weeks after exposure to the virus, which could have provided a level of protection from disease," Neeland said.
Until now, it hasn't been clear why children tend to have milder COVID-19 than adults, according to the researchers.
"Children are less likely to become infected with the virus and up to a third are asymptomatic, which is strikingly different to the higher prevalence and severity observed in children for most other respiratory viruses," Neeland said.
"Understanding the underlying age-related differences in the severity of COVID-19 will provide important insights and opportunities for prevention and treatment, both for COVID-19 and possible future pandemics," she added.
The American Academy of Pediatrics has more on COVID-19.
SOURCE: Murdoch Children's Research Institute, news release, Feb. 17, 2021