COVID-19 vaccine uptake and effectiveness among people with recent history of injection drug use in British Columbia, Canada: A retrospective analysis
Bibliographic record
Abstract
BACKGROUND: It is a public health priority to assess vaccine impact in marginalized populations disproportionately affected by COVID-19 to inform population-specific policies and reduce health disparities. We assessed COVID-19 vaccine uptake and effectiveness among people who inject drugs (PWID) in British Columbia, Canada. METHODS: We used a population-based, linked data platform and a validated algorithm with high specificity to create a cohort of people aged 18-65 years with recent history of injection drug use (PWID). Vaccine uptake was assessed from Dec 15, 2020 (vaccine rollout) to the end of 2022. mRNA vaccine effectiveness against infection and severe outcomes was estimated using the test-negative study design during a period of Delta emergence/predominance (May 30th, 2021 to Nov 27th, 2021). We matched non-PWID to PWID on sociodemographics to create a comparison group. RESULTS: The cohort included 26,581 PWID, of whom a subset (1188 test-positive cases, 169 severe outcomes) were included in vaccine effectiveness analyses. By the end of 2022, the percentage of PWID vs. non-PWID who had received a vaccine dose was 72.6 % vs. 83.0 % (1st dose) and 64.7 % vs. 81.1 % (2nd dose). Vaccine effectiveness within 7-179 days after 2nd dose among PWID was 80.0 % (95 % CI 76.1-83.3 %) against infection and 92.9 % (95 % CI 88.2-95.7 %) against severe outcomes. Equivalent estimates for non-PWID were 90.0 % (95 %CI 89.3-90.7 %) and 98.7 % (95 %CI 98.1-99.2 %). CONCLUSIONS: Vaccine uptake and effectiveness were substantial among people with recent history of injection drug use, but somewhat lower relative to non-PWID matched on sociodemographic characteristics. While results suggest vaccines likely played a large role in reducing the population-level impact of COVID-19 among PWID, our results also highlight a potentially avoidable excess disease burden. Results should be interpreted within the context of the pervasive marginalization of people who use drugs. Findings may also have implications for vaccine outreach efforts and booster dose prioritisation.
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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 | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.007 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".