Memory CD4 T cells generated after infection with OC43, a common cold coronavirus, also exhibited an immune response against SARS-CoV-2 in early childhood, according to results from 2- and 6-year-old children and adults who did not have antibodies against the novel coronavirus and from a group of adults who had recovered from COVID-19. By age 2 years, many children had antibodies against OC43; by age 6, the reactivity of the CD4 T cells had peaked and then declined in adulthood.
Source: JAMA Online First