Serological Profile of COVID-19 in Children with Comorbidities during Omicron Variant Circulation

Тhe characteristics of the humoral immune response to SARS-CoV-2 in children, particularly those with comorbid conditions, remain incompletely understood. The observed variability in antibody production and the sensitivity of serological assays complicate the objective assessment of seroconversion in the pediatric population.

Objective: To determine the qualitative and quantitative profiles of IgM and IgG antibodies against SARS-CoV-2 in children with somatic comorbidities during the acute phase of COVID-19 amid the circulation of the Omicron variant.

Materials and Methods: A prospective, single-center, non-randomized cohort study was conducted involving hospitalized children with confirmed COVID-19 and underlying chronic conditions. Serological testing was performed on days 1, 8, and 14 of illness using enzyme-linked immunosorbent assay (ELISA) and immunochemiluminescence assay (ICLA) to measure IgM and IgG levels.

Results: A total of 99 children with comorbidities were included in the analysis. The seropositivity rate for IgM remained low at all time points (up to 26.3% on day 14). IgG antibodies were detected in the majority of patients as early as day 1, with ELISA demonstrating higher sensitivity (77.6%) compared to ICLA (60%), peak IgG levels were observed on day 8, followed by a significant decline by day 14 (p < 0.01). Children with respiratory system diseases exhibited statistically higher IgG levels compared to those with hemoblastoses, solid tumors, primary immunodeficiencies, and nervous system disorders.

Conclusions: Serological diagnosis of COVID-19 in children with comorbidities requires careful consideration of the testing method, disease timeline, and type of underlying somatic pathology. IgG antibodies serve as a more informative marker than IgM, with ELISA offering superior sensitivity. 

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