1. Omicron incidence and seroprevalence among children in Montreal, Canada, in early 2023: final results from the longitudinal EnCORE serology study.
- Author
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Charland K, Pierce L, Saucier A, Hamelin MÈ, Barbosa Da Torre M, Carbonneau J, Nguyen CT, De Serres G, Papenburg J, Boivin G, Quach C, and Zinszer K
- Subjects
- Humans, Seroepidemiologic Studies, Child, Incidence, Child, Preschool, Adolescent, Male, Longitudinal Studies, Female, Quebec epidemiology, Antibodies, Viral blood, COVID-19 epidemiology, SARS-CoV-2 immunology
- Abstract
Since early 2022, routine testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) based on symptoms and exposure history has largely ceased in Canada. Consequently, seroprevalence studies, particularly longitudinal studies, have become critical for monitoring the rate of incident SARS-CoV-2 infections and the proportion of the population with evidence of immunity. EnCORE is a longitudinal SARS-CoV-2 seroprevalence study comprising five rounds of serology testing from October 2020 to June 2023, in a sample of 2- to 17-year-olds (at baseline), recruited from daycares and schools in four neighbourhoods of Montreal, Canada. We report on SARS-CoV-2 incidence and seroprevalence among the 509 participants in the fifth and final round of the study. Seroprevalence of antibodies from either infection or vaccination was 98% (95 per cent confidence interval [CI]: 97, 99). The infection-acquired seroprevalence was 78% (95% CI: 73-82), and the incidence rate was 113 per 100 person-years (95% CI: 94-132), compared to the seroprevalence of 58% and the incidence rate of 133 per 100 person-years, respectively, in the fourth round of testing (mid-late 2022). Of the 131 participants newly seropositive for infection in Round 4, only 18 were seronegative for infection in Round 5 (median follow-up: 326 days).
- Published
- 2024
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