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. 2024 Dec;115(6):913-923.
doi: 10.17269/s41997-024-00916-3. Epub 2024 Aug 21.

Seroprevalence of SARS-CoV-2 antibodies among children receiving primary care in Toronto, Ontario

Mary Aglipay  1   2 , Jeffrey C Kwong  1   3   4   5   6   7 , Karen Colwill  8 , Anne-Claude Gringas  8 , Ashleigh Tuite  1 , Muhammad Mamdani  2   3   9   10 , Charles Keown-Stoneman  1   2 , Catherine Birken  9   11   12   13   14 , Jonathon Maguire  15   16   17   18 ; TARGet Kids! Collaboration
Collaborators, Affiliations

Seroprevalence of SARS-CoV-2 antibodies among children receiving primary care in Toronto, Ontario

Mary Aglipay et al. Can J Public Health. 2024 Dec.

Abstract
in English, French

Objective: Characterizing the seroprevalence of SARS-CoV-2 antibodies in children is needed to optimize the COVID-19 public health response. We quantified the seroprevalence of SARS-CoV-2 infection-acquired antibodies and vaccine-acquired antibodies among children receiving primary care in Toronto, Canada.

Methods: We conducted a longitudinal cohort study between January 2021 and November 2022 in healthy children aged 0-16 years receiving primary care in Toronto. The primary and secondary outcomes were seroprevalence of SARS-COV-2 infection-acquired antibodies and vaccine-acquired antibodies ascertained from finger-prick dried blood spots. Samples were tested using an enzyme-linked immunosorbent assay for antibodies to full-length spike trimer and nucleocapsid. We explored sociodemographic differences with Firth's penalized generalized estimating equations.

Results: Of the 475 participants, 50.1% were girls and mean age was 6.4 years (SD = 3.2). We identified 103 children seropositive for infection-acquired antibodies, with a crude seroprevalence that rose from 2.6% (95%CI 1.39-4.92) from January to July 2021 to 50.7% (95%CI 39.5-61.8) by July to November 2022. Seroprevalence of vaccine-acquired antibodies was 45.2% by July to November 2022 (95%CI 34.3-56.58). No differences in sociodemographic factors (age, sex, income, or ethnicity) were identified for infection-acquired antibodies; however, children with vaccine-acquired antibodies were more likely to be older, have mothers with university education, and have mothers who had also been vaccinated.

Conclusion: Our results provide a benchmark for seroprevalence of SARS-CoV-2 antibodies in children in Toronto. Ongoing monitoring of the serological status of children is important, particularly with the emergence of new variants of concern, low vaccine coverage, and discontinuation of PCR testing.

RéSUMé: OBJECTIF: Caractériser la séroprévalence des anticorps du SRAS-CoV-2 chez les enfants est nécessaire pour optimiser la réponse de santé publique à COVID-19. Nous avons quantifié la séroprévalence des anticorps acquis par l’infection au SRAS-CoV-2 et des anticorps acquis par le vaccin chez les enfants recevant des soins primaires à Toronto, au Canada. MéTHODES: Nous avons mené une étude de cohorte longitudinale entre janvier 2021 et novembre 2022 auprès d’enfants en bonne santé âgés de 0 à 16 ans recevant des soins primaires à Toronto. Les résultats principaux et secondaires étaient la séroprévalence des anticorps acquis par l’infection du SRAS-CoV-2 et des anticorps acquis par le vaccin déterminés à partir de taches de sang séché par piqûre au doigt. Les échantillons ont été testés à l’aide d’un test immuno-enzymatique pour détecter les anticorps dirigés contre le trimère de pointe complet et la nucléocapside. Nous avons exploré les différences sociodémographiques à l’aide des équations d’estimation généralisées pénalisées de Firth. RéSULTATS: Sur les 475 participants, 50,1 % étaient des filles et l’âge moyen était de 6,4 ans (ET = 3,2). Nous avons identifié 103 enfants séropositifs aux anticorps acquis lors d’une infection, avec une séroprévalence non ajusté qui est passée de 2,6 % (IC 95% : 1,39–4,92) de janvier à juillet 2021 à 50,7 % (IC 95% : 39,5–61,8) de juillet à novembre 2022. La séroprévalence des anticorps acquis par le vaccin était de 45,2 % de juillet à novembre 2022 (IC à 95% : 34,3–56,58). Aucune différence dans les facteurs sociodémographiques (âge, sexe, revenu ou appartenance ethnique) n’a été identifiée pour les anticorps acquis lors d’une infection; cependant, les enfants avec des anticorps acquis par le vaccin étaient plus susceptibles d’être plus âgés, d’avoir des mères ayant fait des études universitaires et d’avoir des mères également vaccinées. CONCLUSION: Nos résultats fournissent une référence pour la séroprévalence des anticorps du SRAS-CoV-2 chez les enfants de Toronto. La surveillance continue du statut sérologique des enfants est importante, en particulier avec l’émergence de nouveaux variants préoccupants, la faible couverture vaccinale et l’arrêt des tests PCR.

Keywords: Antibody; COVID-19; Children; Primary care; SARS-CoV-2; Seroprevalence; Toronto; Vaccination.

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Conflict of interest statement

Declarations. Conflict of interest: The authors declare no competing interests. Ethics approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional (REB# 20–080 Unity Health Toronto Research Ethics) and national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Consent to participate: Informed consent was obtained from all individual participants included in the study.

Figures

Fig. 1
Fig. 1
Seroprevalence of a infection-acquired antibodies, b vaccine-acquired antibodies, c either infection- or vaccine-acquired antibodies among TARGET Kids! children aged 0–16 years in Toronto, Ontario
See this image and copyright information in PMC

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