Symptomatic and Asymptomatic Transmission of SARS-CoV-2 in K-12 Schools, British Columbia, Canada April to June 2021

Choi, Alex; Mâsse, Louise C.; Bardwell, Samantha; Kayda, Iryna; Zhao, Yanjie; Xu, Yang; Markarian, Ani; Coombs, Daniel; Macdonald, Adrienne; Watts, Allison W.; Dhillon, Nalin; Irvine, Michael; O’Reilly, Collette; Lavoie, Pascal; Goldfarb, David M.

doi:10.1128/spectrum.00622-22

Cited by 6 publications

(4 citation statements)

References 10 publications

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“…Thus, it is important to provide tangible evidence to support or refute public claims. Despite frequent COVID-19 exposures in schools the data here support that many school COVID-19 cases were acquired outside, rather than within the school setting 8 27 28…”

Section: Discussionsupporting

confidence: 55%

SARS-CoV-2 cross-sectional seroprevalence study among public school staff in Metro Vancouver after the first Omicron wave in British Columbia, Canada

et al. 2023

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ObjectiveTo determine the SARS-CoV-2 seroprevalence among school workers within the Greater Vancouver area, British Columbia, Canada, after the first Omicron wave.DesignCross-sectional study by online questionnaire, with blood serology testing.SettingThree main school districts (Vancouver, Richmond and Delta) in the Vancouver metropolitan area.ParticipantsActive school staff enrolled from January to April 2022, with serology testing between 27 January and 8 April 2022. Seroprevalence estimates were compared with data obtained from Canadian blood donors weighted over the same sampling period, age, sex and postal code distribution.Primary and secondary outcomesSARS-CoV-2 nucleocapsid antibody testing results adjusted for test sensitivity and specificity, and regional variation across school districts using Bayesian models.ResultsOf 1850 school staff enrolled, 65.8% (1214/1845) reported close contact with a COVID-19 case outside the household. Of those close contacts, 51.5% (625/1214) were a student and 54.9% (666/1214) were a coworker. Cumulative incidence of COVID-19 positive testing by self-reported nucleic acid or rapid antigen testing since the beginning of the pandemic was 15.8% (291/1845). In a representative sample of 1620 school staff who completed serology testing (87.6%), the adjusted seroprevalence was 26.5% (95% CrI 23.9% to 29.3%), compared with 32.4% (95% CrI 30.6% to 34.5%) among 7164 blood donors.ConclusionDespite frequent COVID-19 exposures reported, SARS-CoV-2 seroprevalence among school staff in this setting remained no greater than the community reference group. Results are consistent with the premise that many infections were acquired outside the school setting, even with Omicron.

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Section: Discussionsupporting

confidence: 55%

SARS-CoV-2 cross-sectional seroprevalence study among public school staff in Metro Vancouver after the first Omicron wave in British Columbia, Canada

et al. 2023

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“…At the start of the pandemic, children were rarely infected, and if they were infected, they had a lower transmissibility than adults [18]. Previous studies have revealed that little transmission has taken place in schools during the pandemic [18,19]. During our study period schools mostly used precautionary measures such as quarantine and homeschooling.…”

Section: Principal Findingsmentioning

confidence: 90%

Lower transmissibility of SARS-CoV-2 among asymptomatic cases: evidence from contact tracing data in Oslo, Norway

Methi

Madslien

2022

BMC Med

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Background Asymptomatic COVID-19 cases have complicated the surveillance and tracking of the pandemic. Previous studies have estimated that 15–25% of all infectees remain asymptomatic. Methods Based on contact tracing data from Oslo, Norway, we estimated transmission and susceptibility dynamics among symptomatic and asymptomatic cases and their contacts as identified by manual contact tracing between September 1, 2020, and September 1, 2021. Results Among 27,473 indexes and 164,153 registered contacts, the secondary attack rate (SAR-14) was estimated to be 28% lower through asymptomatic exposure (13%) compared to symptomatic exposure (18%). Furthermore, those infected by asymptomatic cases were almost three times more likely to be asymptomatic compared to those infected by symptomatic cases. Conclusions Symptomatic cases spread the virus to a greater extent than asymptomatic, and infectees are more likely to be asymptomatic if their assumed infector was asymptomatic.

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“…These results are also in keeping with other seroprevalence and contact tracing studies conducted in BC school settings that showed low rates of SARS-CoV-2 transmission. [15][16][17][18][19] We demonstrated a higher seropositivity among infants and young adults compared with schoolaged children. Our findings contrast with other cohorts in which seropositivity has been reported.…”

Section: Anti-s Igg Concentrationsmentioning

confidence: 60%

“…The copyright holder for this preprint this version posted August 18, 2023. ; https://doi.org/10.1101/2023.08.13.23294036 doi: medRxiv preprint Enrollment for each phase was based on five, 5-year age brackets (0-4, 5-9, 10-14, [15][16][17][18][19][20][21][22][23][24]. There was a target sample size of 500 participants per 5-year age group, per phase; each phase was completed when target sample size was reached.…”

Section: (Which Was Not Certified By Peer Review)mentioning

confidence: 99%

Factors associated with severe acute respiratory syndrome-related coronavirus 2 infection in unvaccinated children and young adults

Silverberg

Shulha

McMillan

et al. 2023

Preprint

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BACKGROUND: Pediatric COVID-19 cases are often mild or asymptomatic, which has complicated estimations of disease burden using existing testing practices. We aimed to determine the age-specific population seropositivity and risk factors of SARS-CoV-2 seropositivity among children and young adults during the pandemic in British Columbia (BC). METHODS: We conducted two cross-sectional serosurveys: phase 1 enrolled children and adults <25 years between November 2020-May 2021 and phase 2 enrolled children <10 years between June 2021-May 2022 in BC. Participants completed electronic surveys and self-collected finger-prick dried blood spot (DBS) samples. Samples were tested for immunoglobulin G antibodies against ancestral spike protein (S). Descriptive statistics from survey data were reported and two multivariable analyses were conducted to evaluate factors associated with seropositivity. RESULTS: A total of 2864 participants were enrolled, of which 95/2167 (4.4%) participants were S-seropositive in phase 1 across all ages, and 61/697 (8.8%) unvaccinated children aged under ten years were S-seropositive in phase 2. Overall, South Asian participants had a higher seropositivity than other ethnicities (13.5% vs. 5.2%). Of 156 seropositive participants in both phases, 120 had no prior positive SARS-CoV-2 test. Young infants and young adults had the highest reported seropositivity rates (7.0% and 7.2% respectively vs. 3.0-5.6% across other age groups). CONCLUSION: SARS-CoV-2 seropositivity among unvaccinated children and young adults was low in May 2022, and South Asians were disproportionately infected. This work demonstrates the need for improved diagnostics and reporting strategies that account for age-specific differences in pandemic dynamics and acceptability of testing mechanisms.

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Symptomatic and Asymptomatic Transmission of SARS-CoV-2 in K-12 Schools, British Columbia, Canada April to June 2021

Cited by 6 publications

References 10 publications

SARS-CoV-2 cross-sectional seroprevalence study among public school staff in Metro Vancouver after the first Omicron wave in British Columbia, Canada

SARS-CoV-2 cross-sectional seroprevalence study among public school staff in Metro Vancouver after the first Omicron wave in British Columbia, Canada

Lower transmissibility of SARS-CoV-2 among asymptomatic cases: evidence from contact tracing data in Oslo, Norway

Factors associated with severe acute respiratory syndrome-related coronavirus 2 infection in unvaccinated children and young adults

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