Effectiveness of COVID-19 vaccines against B.1.617.2 (delta) variant: A systematic review
Bibliographic record
Abstract
Introduction: The coronavirus disease 2019 (COVID-19) pandemic continues to inflict significant morbidity and mortality globally. The asymmetric distribution of vaccines continues to foment the emergence of more transmissible SARS-CoV-2 variants of concern (VOC). Research has shown a reduction in vaccine effectiveness (VE) against these variants, with the most recent being the B.1.617.2 (Delta) variant. The aim of this systematic review is to synthesize COVID-19 VE estimates and their 95% confidence intervals (95% CI) against SARS-CoV-2 Delta variant infection, symptomatic disease, and hospitalization. An updated synthesis of VE estimates against Delta variant is necessary to inform clinical decision-making, policy decisions, and promote vaccine development to protect against future variants. Methods: A comprehensive literature search was conducted using the Ovid-MEDLINE database on October 16, 2021. Observational studies examining VE of WHO-approved COVID-19 vaccines were included. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the non-randomized observational studies included in this review. Results: Eleven studies met eligibility criteria to be included in the review. Overall VE estimates against SARS-CoV-2 Delta variant infection for WHO-approved vaccines reported in this review ranged from 59% [95% CI: 16, 81.6] to 75% [95% CI: 71, 78]. VE against symptomatic Delta variant infection was reported as 79.6 [76.7, 82.1]. Overall VE against Delta variant hospitalization ranged from 86% [95% CI: 82, 89] to 93% [95% CI: 84, 96]. VE against specific vaccines was also reported. Conclusions: Studies included in this review provide evidence that VE against the Delta variant of SARS-CoV-2 is less than VE against previous VOC and wild type SARS-CoV-2 for preventing infection, symptomatic disease and hospitalization. This review demonstrates the vital need for continuous surveillance of VE so that vaccine programs are dynamic and adaptable to the epidemiology of COVID-19. Subsequent research is necessary to examine if the primary reason for reduced VE is VOC immune evasion or waning immunity due to time. This review is relevant to public health practice because it can inform how vaccine programs should adapt to the dynamic nature SARS-CoV-2, in measures such recommending booster doses for certain populations.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".