Humoral cross-reactivity towards SARS-CoV-2 in young children with acute respiratory infection with low-pathogenicity coronaviruses

Background: SARS-CoV-2 infection in children frequently leads to only asymptomatic and mild infections. It has been suggested that frequent infections due to low-pathogenicity coronaviruses in children, impart immunity against SARS-CoV-2 in this age group. Methods: From a prospective birth cohort study prior to the pandemic, we identified children with proven low-pathogenicity coronavirus infections. Convalescent sera from these children were tested for antibodies against respective seasonal coronaviruses (OC43, NL63, and 229E) and SARS-CoV-2 by immunofluorescence and virus microneutralization assay respectively. Results: Forty-two children with proven seasonal coronavirus infection were included. Convalescent sera from these samples demonstrated antibodies against the respective seasonal coronaviruses. Of these, 40 serum samples showed no significant neutralization of SARS-CoV-2, while 2 samples showed inconclusive results. Conclusion: These findings suggest that the antibodies generated in low-pathogenicity coronavirus infections offer no protection from SARS-CoV-2 infection in young children.