Covid-19: children exposed to the virus can develop immunity without being infected
In a clinical case study, researchers reported observing immunity in children who were not infected but whose parents tested positive and had Covid-19.
At a time when we were wondering about immunity to the Sars-CoV-2 coronavirus, a new study suggests that exposure to the virus, without infection, is enough to develop an immune response in children. Clearly, it could be that being in contact with a person who tests positive is enough for children to develop immunity, without becoming infected. This hypothesis comes from a clinical case study, presented by physicians from the Murdoch Childrens Research Institute (MCRI, Melbourne, Australia), and published in the journal Nature Communications.
The study was conducted in a family in which both parents tested positive for coronavirus and developed symptoms (cough, nasal congestion, fever, headache). Researchers have closely followed the couples three school-age children. They took samples of blood, saliva, stool and urine, as well as nasal secretions from each member of the family every two to three days.
Verdict: The researchers found specific antibodies against Sars-CoV-2 in the saliva of all family members, and in detailed serological tests compared with those of healthy controls, not exposed to the virus.
"The youngest child, who had no symptoms, had the strongest antibody response," said Dr. Melanie Neeland of MCRI, a co-author of the study. "Despite the active response of immune cells in all children, the levels of cytokines, molecular messengers in the blood that can trigger an inflammatory response, have remained low. It was consistent with their mild or absent symptoms," she added.
For the scientists, these data raise the possibility that immunity to coronavirus in children may by itself prevent the establishment of Sars-CoV-2 infection. The virus barely has time to contact and infect the body when the immunity is already there.