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

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