How does the child’s immune system react to Covid-19? Apparently, compared to adults, children are infected less often, have mild or asymptomatic courses more often and still produce more specific antibodies that protect them from re-infection. This is shown by a study from Baden-Württemberg that has now been published as a preprint. According to the study, however, cross-protection with harmless cold coronaviruses does not play a role.
What role do children play in the Covid 19 pandemic? How easily do they get infected, how high is their risk of severe disease and how well are they protected after an infection? The answers to these questions are important for political decisions, for example when it comes to the extent to which school closings are necessary and whether children should be vaccinated against Sars-CoV-2. However, the data situation on children and Covid-19 is still very limited.
Children become infected less often
A team led by Hanna Renk from the Tübingen University Hospital examined 328 families in which at least one family member fell ill during the first Covid-19 wave over the course of a year. The researchers recorded which family members were infected, which symptoms they had and how strong their immune response was in the following months. A total of 548 children between the ages of six and 14 years and 717 adults took part in the study. The researchers found that children were significantly less likely to be infected from their infected family member than adults: In the participating families, only 34 percent of children, but 58 percent of adults, were infected.
In addition, almost half of the sick children had no symptoms. In adults, however, only nine percent of the infections were asymptomatic. Even in participants with symptoms, however, the disease was mild in most cases. However, the nature of the symptoms differed between children and adults: while fever, cough, diarrhea and taste disorders were equally good indicators of infection in adults, only taste disorders were a good indicator in children. “These findings suggest that the symptom criteria used for the subsequent PCR test must be different for children and adults,” the researchers write.
Antibody protection for one year
Twice during the course of the study – three to four months and eleven to twelve months after the first illness in the family – the researchers took blood from all family members and examined the antibody levels against Sars-CoV-2 and against various harmless cold coronaviruses. “Although the infection was asymptomatic more often in children, they had higher specific antibody levels than the adults,” the researchers report. It made no difference to antibody levels in either children or adults whether or not they had symptoms during their infection. In the blood test after eleven to twelve months, the researchers found that the antibody response in children was apparently more stable than in adults: almost a year after infection, 96 percent of the children had an antibody titer high enough for immunization. In the case of adults, it was only 82 percent. The antibodies of the children and adults were also effective against different virus variants.
The researchers also examined to what extent it plays a role in antibody production whether the immune system had previously had contact with related but harmless coronaviruses. “Although cross-protection between Sars-CoV-2 and other human coronaviruses was suspected, our analyzes did not find any evidence of such effects,” they report. The antibodies against harmless cold coronaviruses had no influence on whether a person was infected with CovidD-19 or on how the antibody level against Sars-CoV-2 developed. “This strongly suggests that the lower incidence of Sars-CoV-2 infections in children is not due to cross-protection,” said the researchers.
The results on antibody titers in children could also influence future policy decisions. “Although Sars-CoV-2 infections in children are usually mild or even asymptomatic, they show a strong and sustained immune response,” the researchers summarize. “This speaks in favor of long-term protection after infection and could influence the design of vaccination strategies for children who have recovered from Covid-19.”
Source: Hanna Renk (Clinic for Pediatrics and Adolescent Medicine, University Hospital Tübingen) et al., MedRxiv, doi: 10.1101 / 2021.07.20.21260863