immunity without having been sick for almost one in two children

THE ESSENTIAL

  • Children would be much more likely to develop cross-reacting antibodies than adults.
  • Chronic exposure to the virus causes children’s immune systems to develop protective systems, in this case antibodies, to guard against infection.

Does immunity progress faster than you think? Two studies recently published in leading scientific journals suggest that many children have developed immunity to the virus without being infected with it. The first, published on November 6 in the review Science, estimates that 44% of children have developed effective antibodies against Covid-19 without even having been infected. British researchers claim that exposure to other coronaviruses led their bodies to develop an effective immune response against the new coronavirus SARS-CoV-2. The second study, presented on November 11 in the journal Nature Communications, claims that some children have developed an immune response following chronic exposure to the SARS-CoV-2 virus from their parents.

Children better protected than adults

Exposure to other coronaviruses would protect nearly one in two children against infection with the new coronavirus SARS-CoV-2. British researchers conducted a study of 302 minors, comparing the blood results of patients with the virus to those of volunteers who did not catch it. They found that 43.8% of children and adolescents aged 1 to 16 who have not contracted the virus carry IgG antibodies that protect against infection with Covid-19.

The researchers believe that these results are important in the fight against the pandemic. “Our results show that children are much more likely to develop cross-reacting antibodies than adults, continues Kevin Ng, author of the study. More research is needed to understand why, but it could be because children are more regularly exposed to other coronaviruses.”

This additional research must show, in particular, why adults who have been exposed to other coronaviruses during their life have not retained the antibodies that could protect them against Covid-19. Dr. Stephen J. Elledge, professor of genetics at Harvard Medical School, estimated at New York Times that these antibodies and the memory cells that accompany them disappear over time.

No infection but antibodies

The family is believed to play an important role in the formation of effective antibodies against Covid-19 in children. Australian researchers from the Murdoch Children’s Research Institute (MCRI) have shown that continued contact with their parents infected with the virus led their bodies to develop these antibodies despite negative screening results in these children. The study authors examined the immune profile of a Melbourne family of two parents with Covid-19 with symptoms and their three children of primary school age. Blood, saliva, nose and throat, stool and urine samples were taken from the family every 2-3 days. The researchers found specific antibodies to SARS-CoV-2 in the saliva of all family members and in detailed serological tests against healthy controls.

The youngest child, who showed no symptoms, had the strongest antibody response, wondered Dr Melanie Neeland of MCRI. Despite the active immune cell response in all children, levels of cytokines, molecular messengers in the blood that can trigger an inflammatory response, have remained low. This was consistent with their mild or absent symptoms.”

The researchers suggest that this study shows that chronic exposure to the virus causes children’s immune systems to develop protective systems, in this case antibodies, to guard against infection. “Studying immune responses to SARS-CoV-2 in all age groups is essential for understanding disease susceptibility, differences in severity, and vaccine candidates”, Concluded Nigel Craworf, professor at MCRI.


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