Follow-up study on seasonal coronavirus infection and reinfection. Serological follow-up study indicates high seasonal coronavirus infection and reinfection rates in early childhood

Seasonal human coronaviruses (HCOVs) cause respiratory infections, especially in children. Currently, the knowledge on early childhood seasonal coronavirus infections and on the duration of antibody levels following the first infections is limited. Here we analysed serological follow-up samples to estimate the rate of primary infection and reinfection(s) caused by seasonal coronaviruses in early childhood. Serum specimens were collected from 140 children at ages of 13, 24 and 48 months, and IgG antibody levels against recombinant hCoV nucleoproteins were measured by enzyme immunoassay (EIA). Altogether, 84% (118/140) of the children were seropositive for at least one seasonal coronavirus nucleoprotein by the age of 3 years. Cumulative seroprevalence for HCOVs 229E, HKU1, NL63 and OC43 increased by age and was 46%, 28%, 71% and 44%, respectively, at the age of 3 years. Increased antibody levels between yearly samples indicated reinfections by 229E, NL63 and OC43 viruses in 20-48% of previously seropositive children by the age of 3 years. A mean decline of 50-74% or 20-66% in antibody levels were observed in initially seropositive children at 1 or 2 years of age, respectively, in case there was no reinfection by the age of 3 years. Correlation of EIA results for 229E and NL63 as well as for OC43 and HKU1 suggested potential cross-reactivity between the antibodies. The data shows that seasonal coronavirus infections and reinfections are common in early childhood and the antibody levels decline relatively rapidly.