This work, published in the scientific journal Jama, could provide part of the answer to a question still actively studied by scientists: why are children less affected by the symptomatic forms of Covid-19?
Antibodies are naturally produced by the body in the presence of a virus in order to fight against it and get rid of it.
The researchers analyzed more than 31,000 serological tests (measuring the presence of antibodies in the blood) carried out in New York between April and August 2020. They focused on those which tested positive, and therefore indicating a past infection with Covid -19.
According to their results, children between 1 and 10 years of age developed a median level of IgG antibodies (for immunoglobulins G, the class of antibodies most present in the blood), “significantly higher” than in adults.
In addition, the lowest IgG antibody levels were observed in young adults aged 19 to 30, before rising with age, for reasons “which remain unclear”, according to the authors.
Further analyzes were carried out on a smaller number of blood samples taken from children, adolescents and young adults, in order to better compare the immune response between these populations.
The median level of IgG antibodies was found to be twice as high in children between 1 and 10 years old as in adolescents (11 to 18 years old), who themselves were twice as high as in young adults ( 19 to 24 years old).
“Our results suggest that the differences in the clinical manifestations of Covid-19 in pediatric patients (children, editor’s note) compared to those in adult patients, could in part be due to an age-related immune response”, write the authors.
“Our data may partly explain the overall lower level of symptoms and severe cases of the disease in infected children,” they add.
Another point to note: serological tests were found to be positive for a similar proportion of children and adolescents than adults. This suggests that children, even if they get less sick from it, “could represent a significant reservoir of transmission” of Covid-19, note the authors.
Last month, a study published in the journal Nature suggested that children defend themselves better against the virus thanks to a better innate immune response, that is to say that intervening in the first line, before acquired immunity ( from which antibodies result).