Signs of Cross-Reactivity Between SARS-CoV-2 and Other Coronaviruses in a Pre-Vaccine Swedish School Setting

This pilot study explored signs of immunological cross-reactivity between SARS-CoV-2 and human coronaviruses (HCoVs) in a Swedish school setting.

A cross-sectional, hypothesis-generating study was conducted late 2020 before vaccines against COVID-19 were available. Forty-seven 7-8-year-old children, seventy-five 14-year-old adolescents, fifty-four 17-year-old adolescents, and 52 adult school staff were included, and immune responses to SARS-CoV-2 and HCoVs were assessed.

The SARS-CoV-2 seroprevalence was high in the older age groups (33%-41%). Seropositive individuals had significantly higher levels of antibodies against betacorona virus compared to seronegative individuals. SARS-CoV-2 seropositivity was rare among the 7-8-year-old children despite the high endemic context. SARS-CoV-2-specific T-cell responses in the absence of SARS-CoV-2-specific antibodies were seen in all age groups.

The data support a role for cross-reactive immune responses induced by recent HCoV infections, with cross-reactive T-cell responses providing protection against COVID-19 in young children.