Children infected with SARS-CoV-2 are often asymptomatic or have mild symptoms. The studies on the seroprevalence kinetics of SARS-CoV-2 antibodies in children are limited. We conducted a cross-sectional survey of the positive rate of the SARS-CoV-2 IgG in pediatric patients without suspected COVID-19 infection between January 2007 and March 2022. We defined the serum samples from the pre-pandemic and pandemic groups (1st-6th waves). Totally, 2557 samples were collected and no samples from the pre-pandemic group or the 1st-4th waves were positive for IgG. There were 4/661 and 16/373 positives at the 5th and 6th waves, respectively. At the 5th wave, the prevalence of IgG was 1.3% in children aged 1-4 years. At the 6th wave, in children <1 year of age, the prevalence was 4.0%, and 2.4%, 5.3%, 5.2% and 10% in age groups 1-4, 5-9, 10-14 and 15-18 years, respectively. In conclusions, the pre-pandemic samples were negative, and the IgG positivity increased during the later period of the pandemic.
Keywords: COVID-19 pandemic; Children; SARS-CoV-2 antibody; Seroprevalence.
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