Seroprevalence of SARS‐CoV‐2 infections among children visiting a hospital

IMPORTANCE: In this study, we retrospectively investigated the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) antibodies within serum samples from children in Beijing, China. These findings provide preliminary guidance regarding population susceptibility to SARS‐CoV‐2, which will aid in establishing policy toward coronavirus disease 2019 (COVID‐19) prevention and control. OBJECTIVE: To understand the seropositivity of anti‐SARS‐CoV‐2 IgM/IgG antibodies among children in Beijing, China, evaluate the susceptibility of children in Beijing to SARS‐CoV‐2, and provide prima facie evidence to guide SARS‐CoV‐2 prevention and control. METHODS: IgM/IgG antibody kits (colloidal gold) were used to conduct preliminary screening of SARS‐CoV‐2 IgM/IgG antibodies in serum samples of children who presented to Beijing Children’s Hospital, Capital Medical University, having fever or requiring hospitalization, from March 2020 to August 2020. Statistical analysis of anti‐SARS‐CoV‐2 antibody seropositivity was performed according to the children’s general demographic characteristics, timing of admission to hospital, presence of pneumonia, and viral nucleic acid test results. RESULTS: The study included 19 797 children with both IgM and IgG antibody results. Twenty‐four children had anti‐SARS‐CoV‐2 IgM‐positive results (positive rate of 1.2‰), twelve children had anti‐SARS‐CoV‐2 IgG‐positive results (positive rate of 0.6‰). Viral nucleic acid test results were negative for the above‐mentioned children with positive antibody findings; during the study, two children exhibited positive viral nucleic acid test results, but their anti‐SARS‐CoV‐2 IgM/IgG antibody results were negative. Anti‐SARS‐CoV‐2 IgM antibody seropositivity was higher in the <1‐year‐old group than in the ≥6‐year‐old group. The rates of anti‐SARS‐CoV‐2 IgM seropositivity was highest in August from March to August; IgG results did not significantly differ over time. The rates of anti‐SARS‐CoV‐2 IgM or IgG seropositivity among children with and without suspected pneumonia did not significantly differ between groups. INTERPRETATION: During the study period, the rates of anti‐SARS‐CoV‐2 IgM/IgG antibody seropositivity were low among children who presented to Beijing Children’s Hospital, Capital Medical University. The findings suggest that children in Beijing are generally susceptible to SARS‐CoV‐2 infection; COVID‐19 prevention and control measures should be strengthened to prevent disease in children.