Young children have a different immune response to COVID

An in-depth study of adaptive immune response to SARS-CoV-2 infection concludes that children under 5 years old have a different response compared with older children and adults. The findings make it clear that young children are not “little adults” when it comes to SARS-CoV-2 infection, and that adaptation to immune threats such as the virus develop progressively through childhood to adulthood, according to Benoît Manfroi and colleagues. They examined adaptive immune responses in 89 people, including preschoolers, older children, and adults with mild or severe COVID-19, before, during, and 11 months after infection. Manfroi et al. found that during SARS-CoV-2 infection, children under 5 had a lower and phenotypically different antiviral CD4+ T cell response compared with older children and adults with mild disease. Adults with severe disease also had a distinct CD4+ T cell response that differed from all other groups. After infection, preschoolers had a distinct set of memory T cells with high inflammatory features compared with adults, and fewer virus-reactive memory B cells compared with older children and adults. As the researchers point out, the COVID-19 pandemic provided a unique opportunity to compare specific adaptive immune responses between age groups, because there was no viral-specific immune memory to the novel coronavirus in adults to complicate the comparison.

The study, Preschool-age children maintain a distinct memory CD4+ T cell and memory B cell response after SARS-CoV-2 infection, is published in Science Translational Medicine