Measles seroprevalence among individuals serologically tested in Ontario, Canada
Bibliographic record
Abstract
BACKGROUND: Canada eliminated measles in 1998, but the risk of outbreaks remains due to sub-optimal vaccine coverage and imported cases. To address limitations of vaccine coverage data, we measured measles seroprevalence among a convenience sample of individuals serologically tested in Ontario, Canada. METHODS: We linked measles IgG serology data from 349,451 individuals tested during 2014-2016 to health administrative databases and used a cross-sectional design to measure measles IgG seroprevalence. We estimated seroprevalence overall and by sociodemographic factors. FINDINGS: Using the manufacturer-recommended threshold of ≥275 mIU/mL, measles seroprevalence was 83.5 % (95% CI, 83.4-83.6 %), below the 90-95 % herd immunity threshold. However, using the often cited >120 mIU/mL threshold, seroprevalence was 97.1 % (95% CI, 97.0-97.1 %). Using a threshold of ≥275 mIU/mL, seroprevalence varied by age, with the lowest observed among adolescents aged 12-19 years (75.3 %; 95% CI, 74.8-75.7 %) and young adults aged 20-29 years (75.8 %; 95% CI, 75.5-76.1 %), and highest among the oldest cohorts aged ≥50 years (96.9 %; 95% CI, 96.8-97.0 %). When using a lower threshold of protection (>120 mIU/mL), large differences in seroprevalence by age were not observed. Among individuals born in or after 1985, immigrants had lower seroprevalence (≥275 mIU/mL) (71.0 %; 95% CI, 70.6-71.5 %) compared to those born in Canada (77.8 %; 95% CI, 77.6-78.1 %). INTERPRETATION: The uncertainty of the exact correlate of protection for measles complicates the interpretation of seroprevalence data when assessing whether this convenience sample of individuals serologically tested for measles is adequately protected to prevent future outbreaks. Measles seroprevalence varied significantly by age and immigrant status, with highest seronegativity (<275 mIU/mL) observed among adolescents, young adults, and young immigrants. It is possible that sustaining measles elimination in Ontario will be challenging in the face of ongoing measles importations from abroad, and immunity gaps in some population groups.
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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 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| 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".