Seropositivity of SARS-CoV-2 in an unvaccinated cohort in British Columbia, Canada: a cross-sectional survey with dried blood spot samples
Bibliographic record
Abstract
OBJECTIVES: Gathering population-based data on prevalence of SARS-CoV-2 infection is vital to the public health response and planning. Current seroprevalence data in BC are limited with respect to considerations of how socioeconomic and demographic factors, such as age, sex, gender, income, identifying as a visibility minority and occupation, are related to SARS-CoV-2 antibody detection due to infection-acquired immunity. We aimed to estimate the SARS-CoV-2 seropositivity in a cohort of British Columbians, using at-home self-collected dried blood spot (DBS) samples. DESIGN: This cross-sectional study included online surveys that collected sociodemographic and COVID-19 vaccine receipt information, and an at-home DBS collection kit. SETTING: British Columbia (BC), Canada. PARTICIPANTS: Eligible participants were aged 25-69 years and residents of BC. PRIMARY OUTCOME MEASURE: SARS-CoV-2 anti-spike IgG antibody detection in unvaccinated individuals. Adjusted incidence rate ratios (aIRR) explored factors associated with seropositivity. RESULTS: SARS-CoV-2 serology was performed on a total of 4048 unvaccinated participants 25-69 years of age who submitted DBS samples taken from November 2020 to June 2021. A total of 118 seropositive cases were identified, for an estimated overall seropositivity of 2.92% (95% CI 2.42% to 3.48%). Participants identifying as a visible minority had a higher seropositivity, 5.1% vs 2.6% (p=0.003), compared with non-visible minority participants. After adjustment by age and sex, identifying as a visible minority (aIRR=1.85, 95% CI 1.20 to 2.84) remained the only significant factor associated with SARS-CoV-2 antibody detection in this cohort of unvaccinated individuals. CONCLUSIONS: SARS-CoV-2 seropositivity in the BC population due to infection-acquired immunity was low. Seropositivity indicated that among those unvaccinated, visible minority communities have been most impacted. Continued monitoring of SARS-CoV-2 serology due to both infection-acquired and vaccine-acquired immunity will be vital in public health planning and pandemic response.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".