SARS-CoV-2 Seroprevalence in Children under 5 Years Old-A Regional Seroepidemiological Study.

Background and Objectives: The aim of this research was to assess the spread of SARS-CoV-2 infection; the study was motivated by parental hesitancy regarding child vaccination, and the potential passive immunity of infants acquired through breastfeeding from mothers vaccinated against COVID-19 or infected with SARS-CoV-2. Materials and Methods : We quantified the anti-SARS-CoV-2 immunoglobulin G (IgG) titer in the serum of 743 children under 5 years old, hospitalized between 1 August 2022, and 15 September 2023. Results : Among the participants, 52.76% had an anti-SARS-CoV-2 IgG titer that exceeded the reactivity threshold of the kit used, with an average of 1558.01 U/mL across the entire group. By age-specific categories, SARS-CoV-2 antibody prevalence was 43.04% for 0-12 months, 42.22% for 12-24 months, 61.67% for 24-36 months, 65.17% for 36-48 months, and 68.55% for 48-59 months. Gender analysis revealed 55.32% male participants, with a 52.07% seropositivity rate. Notably, IgG titer correlated positively with the child's age. Gender, admission diagnosis, and emergency department presentation were not variation factors of the IgG titer. Conclusions : The majority of children in the study group demonstrated IgG against SARS-CoV-2, and this rate increased with the child's age. Also, the IgG titer increased with the child's age.