The level of antibodies — and therefore the level of protection — after a COVID-19 infection varies greatly by age. Children remember SARS-CoV-2 less well, which could “probably” make them more vulnerable to reinfection.
A recent study published on JAMA Network indicates that children produce almost half as many antibodies as adults after contracting COVID-19.
This is a “small study which goes in the same direction as several other studies”, confirms Dr. Jesse Papenburg, specialist in pediatric infectiology associated with McGill University.
The reason for this is “complex and unclear”, he says, but can be summed up by simplifying the principle of immunity into two parts.
On the one hand, there is the “innate immune response”. This first line of defense is found in the nose, mouth and throat, ie the first access routes to the body. The cells there can stop the infection as soon as a virus tries to enter the body.
On the other hand, there is “the adapted immune response”. These are the antibodies that are responsible for secondarily eliminating the virus if it succeeds in penetrating all the organs.
Finally, science shows that children have a much stronger innate immune response than adults. A child’s constantly runny nose is perhaps the best example of a constantly activated “innate immune response”.
“For the child, the most important thing is not to be super good at preventing a specific virus, but to be full of different viruses, underlines Dr. Papenburg. In the first years of his life, a child can be in contact with 6 to 10 infections per year. »
Against the virus that causes COVID-19, this rapid response therefore eliminates the infection before it even spreads in the body. Since adults no longer have such a potent “innate” response, they must rely on their antibodies to fight disease.
Risks of reinfections
Since antibodies constitute “a memory of the body” which makes it possible to better fight against a specific virus if it tries a second reinfection, the deficit of these in children opens the door to new infections in the future.
“It’s possible” that reinfections are more common in children, says Dr. Papenburg, although no studies have yet clarified the issue.
Dr. Hélène Decaluwe, clinical researcher at the CHU Sainte-Justine, invites us not to generalize these data from the JAMA Network study. They were extracted from “little or no symptomatic” patients, which is very broad. In addition, this low intensity of the disease causes few antibodies, both in adults and in children, which does not give a complete picture.
All the same, “it’s not really surprising” to see fewer antibodies in children, because they generally cause less symptomatic COVID-19.
“The child may not have a good memory of having seen the virus,” she said. Thus, if another variant arrives, it can re-infect 6 months, 1 year or 2 years later. Hence the importance of vaccination, which stimulates the creation of antibodies directly in the blood and muscles, mentions the pediatric immunologist.
However, there is no need to worry too much about these reinfections, she says, as children have very few serious complications from COVID-19.
His research team is recruiting children and adolescents for a study aimed at establishing their immune response after vaccination.
This text is taken from our newsletter “Coronavirus Mail” of March 21, 2022. To subscribe, click here.