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SARS-CoV-2 seroprevalence among children in Greece during Omicron variant period

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Abstract

The Omicron variant is associated with increased transmissibility, but evidence about the impact of Omicron in seropositivity of children is limited. This study aims to evaluate SARS-CoV-2 seroprevalence in children during the different variants’ subperiods. A prospective multicenter seroprevalence study was conducted in 7 University public hospitals in Greece from November 2021 to August 2022 (3 subperiods: November 2021-February 2022, March 2022-May 2022, June 2022-August 2022). Children from different age groups, admitted to the hospital or examined in outpatient clinics for reasons other than COVID-19 were enrolled. Neutralizing antibodies (Nabs), anti-Spike (anti-S) and anti-nucleocapsid (anti-N) SARS-CoV-2 IgG in serum were evaluated. A total of 2127 children (males:57,2%; median age:4,8years) were enrolled. Anti-N IgG seropositivity increased from 17,8% in the first sub-period to 40,7% in the second sub-period and then decreased in the third sub-period (36,7%). Anti-S IgG seropositivity appeared to have an increasing trend over the study period, starting from 34,8% and reaching 80,7%. Children aged 1–4 years old have significantly higher anti-N IgG titers compared to children aged 0–1 years old (p < 0,001). Infants have significantly lower anti-S IgG titers compared to all other age groups (p < 0,001). Immunocompromised children and infants have the lowest seropositivity for NAbs.

Conclusions During the Omicron period, seropositivity significantly increased, as a result of higher transmissibility. Neonates and infants have lower antibody titers compared to other age groups, while young children aged 1–4 years old present higher antibody titers, suggesting that this age group may mount a higher antibody response. Continuous surveillance seroprevalence studies are needed in children, in order to identify the true extent of SARS-CoV-2 and guide the planning of adequate public health measures.

What is Known:

• Seroprevalence surveys among children may be extremely useful, in order to properly monitor the immunity, either natural or acquired, through the quantification of IgG antibodies and to plan further immunization policies.

• There are variations in the seroprevalence of COVID-19 between the different periods, according to the vaccination rates, the type of circulating variant and the transmissibility of the virus.

• The Omicron variant is associated with increased transmissibility, but evidence about the impact of Omicron in seropositivity of children is limited.

What is New:

• In this large multicenter seroepidemiological study, SARS-CoV-2 seroprevalence rate in children is higher during the Omicron period in comparison to the previous pandemic waves, due to the high transmissibility of the virus and the increased rates of reinfection.

• Neonates and infants have lower antibody titers compared to other age groups, while young children aged 1–4 years old present higher antibody titers, indicating that the children of this age group mount a higher antibody response.

• This study provides essential information about immunity and the level of protection in the pediatric population, as neutralizing antibodies were evaluated, in addition to the anti-N and anti-S IgG antibodies.

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Data availability

No datasets were generated or analysed during the current study.

Abbreviations

anti-N:

anti-Nucleocapsid protein

anti-S:

anti-Spike protein

CMIA:

Chemiluminescent microparticle immunoassay

COVID-19:

Coronavirus disease 2019

ELISA:

Enzyme linked immunoassay

ER:

Emergency room

GMT:

Geometric mean titers

IgG:

Immunoglobulin G

IQR:

Interquartile range

Nabs:

Neutralizing antibodies

SARS-CoV-2:

Severe acute respiratory syndrome coronavirus 2

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Acknowledgements

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Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Author information

Authors and Affiliations

  1. Second Department of Paediatrics, School of Medicine, National and Kapodistrian University of Athens, ‘P. and A. Kyriakou’ Children’s Hospital, Thivon and Leivadias, Athens, 30601, Greece

    Dimitra Dimopoulou, Ariadni Neofytou, Foteini Dasoula, Maria Tampouratzi, Athina Koloi, Eirini Eleftheriou, Theoklis Zaoutis & Maria N. Tsolia

  2. Central Public Health Laboratory, Hellenic Centre for Diseases Control and Prevention, Athens, Greece

    Despoina Sotiri, Garyfallia Loulou, Kalliopi Raptaki & Kyriaki Tryfinopoulou

  3. Center for Clinical Epidemiology and Outcomes Research (CLEO), Athens, 15451, Greece

    Dimitra Kousi

  4. School of Medicine, Department of Paediatrics, University General Hospital of Heraklion, University of Crete, Heraklion, Greece

    Eleni Vergadi & Emmanouil Galanakis

  5. School of Health Sciences, Faculty of Medicine, Department of Paediatrics, University General Hospital of Larissa, University of Thessaly, Larissa, Greece

    Eleni Papadimitriou, Ioanna Grivea & George Syrogiannopoulos

  6. Department of Pediatrics, Venizeleion General Hospital, Heraklion, Greece

    Irini Zorbadaki & Fani Ladomenou

  7. Attikon University Hospital, National and Kapodistrian University of Athens, Third Department of Paediatrics, Athens, Greece

    Artemis Mavridi & Vassiliki Papaevangelou

  8. Medical School, Department of Paediatrics, University of Patras, Patras, Greece

    Konstantinos Miliordos, Evangelia Steletou & Despoina Gkentzi

  9. First Department of Paediatrics, Aghia Sophia’ Children’s Hospital, National and Kapodistrian University of Athens, Athens, Greece

    Maria Strempela, Vassiliki Spoulou & Athanasios Michos

  10. First Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece

    Paraskevi C. Fragkou

Authors
  1. Dimitra Dimopoulou
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  2. Despoina Sotiri
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  16. Evangelia Steletou
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  18. Paraskevi C. Fragkou
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  19. Vassiliki Spoulou
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  21. Despoina Gkentzi
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  22. Vassiliki Papaevangelou
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  23. Fani Ladomenou
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  28. Kyriaki Tryfinopoulou
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  29. Maria N. Tsolia
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Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by DD, MT, DS, DK, GL, KR, AN, FD, MT, AK, EE, EV, EP, IZ, AM, KM, ES, MS and PCV. The first draft of the manuscript was written by DD and MT. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Maria N. Tsolia.

Ethics declarations

Ethics approval

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the institution’s Ethical and Research Committee (approval number:507/20.10.2020).

Consent to participate

Informed consent was obtained from all individual participants included in the study.

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Not applicable.

Competing interests

The authors declare no competing interests.

Additional information

Communicated by Tobias Tenenbaum.

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Dimopoulou, D., Sotiri, D., Kousi, D. et al. SARS-CoV-2 seroprevalence among children in Greece during Omicron variant period. Eur J Pediatr 183, 2491–2499 (2024). https://doi.org/10.1007/s00431-024-05486-7

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