Effectiveness of vaccination against symptomatic and asymptomatic SARS-CoV-2 infection: a systematic review and meta-analysis
Bibliographic record
Abstract
ABSTRACT OBJECTIVE To assess the effectiveness of SARS-CoV-2 vaccines in terms of prevention of disease and transmission. The evaluation was narrowed to two mRNA vaccines and two modified adenovirus vectored vaccines. METHODS A frequentist random effects meta-analysis was carried out after data extraction. Risk of bias of the included studies was assessed using New-Castle-Ottawa Scale. The overall risk of SARS-CoV-2 infection confirmed by real time Polymerase Chain Reaction (PCR) was estimated in partially and fully vaccinated individuals. The effect size was expressed as Relative Risk (RR) and RRR (RR reduction) of SARS-CoV-2 infection after vaccination. Potential sources of heterogeneity were investigated through between-study heterogeneity analysis and subgroup meta-analysis. RESULTS The systematic review identified 27 studies eligible for the quantitative synthesis. Partially vaccinated individuals presented a RRR=73% (95%CI=59%-83%) for any positive SARS-CoV-2 PCR (RR=0.27) and a RRR=79% (95%CI=30%-93%) for symptomatic SARS-CoV-2 PCR (RR=0.21). Fully vaccinated individuals showed a RRR=94% (95%CI=88%-98%) for any SARS-CoV-2 positive PCR (RR=0.06) compared to unvaccinated. According to the subgroup meta-analysis, full BNT162b2 vaccination protocol achieved a RRR=84%-94% against any SARS-CoV-2 positive PCR and a RRR=68%-84% against symptomatic positive PCR. The RR for any SARS-CoV-2 positive PCR remained higher within elderly groups aged ≥69 years (RR=0.12-0.15) compared to younger individuals (RR=0.05-0.12). The RR against B.1.351 infection approached 0.40 for any positive PCR and 0.36 for symptomatic SARS-COV-2 while the RR of any B.1.1.7 infection was 0.14. CONCLUSION The current licensed vaccines may be transmission blocking, especially after full vaccination protocol. Given the substantial heterogeneity, results should be interpreted with caution. Subgroups meta-analyses suggested that the risk of any SARS-CoV-2 infection may be higher for non-B.1.1.7 variants and individuals aged ≥69 years. Further data and longer follow-up are required to investigate additional sources of heterogeneity and the effectiveness of SARS-CoV-2 vaccination within population subgroups. STRENGTHS Real-world data suggest that the current licensed vaccines may be transmission blocking, in particular after full vaccination protocol. The risk of any SARS-CoV-2 infection either symptomatic or asymptomatic, may be higher for non-B.1.1.7 variants and individuals aged ≥69 years. LIMITATIONS Given the substantial heterogeneity encountered in this meta-analysis, results should be interpreted with caution Fur ther evidence on the impact of SARS-CoV-2 variants are vital in order to monitor mutations associated with vaccine escape
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.014 | 0.031 |
| Meta-epidemiology (narrow) | 0.004 | 0.002 |
| Meta-epidemiology (broad) | 0.024 | 0.048 |
| Bibliometrics | 0.007 | 0.006 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 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".