# SARS-CoV-2 Seroepidemiology and Antibody Levels in Children during BA.5 Predominance Period

## TL;DR

This study shows that most children in Athens were exposed to SARS-CoV-2 during the BA.5 Omicron wave, with rising antibody levels over time.

## Contribution

The study provides new insights into pediatric SARS-CoV-2 seroprevalence and highlights the importance of testing for both nucleocapsid and spike antibodies.

## Key findings

- Seropositivity rates in children increased from 70% to 84.8% during the BA.5 period.
- Children aged 6–12 years had the highest seropositivity rates in all study periods.
- 11.4% of Abs-N-seronegative samples were Abs-S-seropositive during period C.

## Abstract

This is a SARS-CoV-2 seroepidemiological study in a pediatric population (0–16 years) during the BA.5 Omicron predominance period in the Athens metropolitan area. Serum samples were tested for SARS-CoV-2 nucleocapsid antibodies (Abs-N), representing natural infection during three periods of BA.5 predominance: 1 May 2022–31 August 2022 (period A), 1 September 2022–31 December 2022 (period B), and July 2023 (period C). Εpidemiological data were also collected. Additionally, in period C, Abs-N-seronegative samples were tested for SARS-CoV-2 spike antibodies (Abs-S). A total of 878 children were tested (males: 52.6%), with a median age (IQR) of 96 (36–156) months; the number of cases of seropositivity during the three periods were as follows: A: 292/417 (70%), B: 288/356 (80.9%), and C: 89/105 (84.8%), with p < 0.001. SARS-CoV-2 seropositivity increased from period A to C for children 0–1 year (p = 0.044), >1–4 years (p = 0.028), and >6–12 years (p = 0.003). Children > 6–12 years had the highest seropositivity rates in all periods (A: 77.3%, B: 91.4%, and C: 95.8%). A significant correlation of monthly median Abs-N titers with monthly seropositivity rates was detected (rs: 0.812, p = 0.008). During period C, 12/105 (11.4%) Abs-S-seropositive and Abs-N-seronegative samples were detected and total seropositivity was estimated at 96.2% (101/105). The findings of this study indicate a high SARS-CoV-2 exposure rate of children during the BA.5 predominance period and suggest that in future seroepidemiological studies, both antibodies should be tested in Abs-N-seronegative populations.