SynthesisEuro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin2021
Effectiveness of COVID-19 vaccines against SARS-CoV-2 infection with the Delta (B.1.617.2) variant: second interim results of a living systematic review and meta-analysis, 1 January to 25 August 2021.
Synthesis in Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 94 papers, 6 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
94 citing papers in PubMed, 6 syntheses or guidelines pooled it.
- Feeding the feelings: gender differences in emotional eating during COVID-19: a systematic review and meta-analysis.Frontiers in nutrition · 2025Pooled it
- A systematic review and meta-analysis of the global prevalence and determinants of COVID-19 vaccine acceptance and uptake in people living with HIV.Nature human behaviour · 2024Pooled it
- Risk factors affecting COVID-19 vaccine effectiveness identified from 290 cross-country observational studies until February 2022: a meta-analysis and meta-regression.BMC medicine · 2022Pooled it
- Effectiveness of COVID-19 vaccines against SARS-CoV-2 variants of concern: a systematic review and meta-analysis.BMC medicine · 2022Pooled it
- Duration of effectiveness of vaccines against SARS-CoV-2 infection and COVID-19 disease: results of a systematic review and meta-regression.Lancet (London, England) · 2022Pooled it
- Therapeutic effects of herbal-medicine combined therapy for COVID-19: A systematic review and meta-analysis of randomized controlled trials.Frontiers in pharmacology · 2022Pooled it
- Persistence of immunity and impact of third dose of inactivated COVID-19 vaccine against emerging variants.Scientific reports · 2022Trial
- Innovative Randomized Phase I Study and Dosing Regimen Selection to Accelerate and Inform Pivotal COVID-19 Trial of Nirmatrelvir.Clinical pharmacology and therapeutics · 2022Trial
- Health, economic, and equity impact of a COVID-19 mobile vaccine clinic program in US: a cost-effectiveness analysis.Lancet regional health. Americas · 2026Article
- Recent developments of vaccines for older adults: Adjuvants and beyond.Human vaccines & immunotherapeutics · 2025Review
- An extension of the Benefit Risk Assessment of VaccinEs toolkit to evaluate Comirnaty and Spikevax vaccination in the European Union.European journal of public health · 2025Article
- Association of COVID-19 infection and COVID-19 vaccination with idiopathic sudden sensorineural hearing loss in Malaysia: a case-control study.BMC public health · 2025Article
- Impact of pharmaceutical and non-pharmaceutical interventions on COVID-19 in Tunisia.BMC public health · 2024Article
- Individual use of self-medication and other remedies in COVID-19 outpatients in Western-Pomerania.Scientific reports · 2024Observational
- Article
- Application of the screening method for estimating COVID-19 vaccine effectiveness using routine surveillance data: Germany's experience during the COVID-19 pandemic, July 2021 to March 2023.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin · 2024Article
- Unbiased immunome characterisation correlates with COVID-19 mRNA vaccine failure in immunocompromised adults.Frontiers in immunology · 2024Article
- Effectiveness of BBV152 vaccine and ChAdOx1-S vaccine in preventing severe disease among vaccinated patients admitted to a designated COVID-19 hospital in India.Clinical and experimental vaccine research · 2024Article
- Article
- Vaccination reduces viral load and accelerates viral clearance in SARS-CoV-2 Delta variant-infected patients.Annals of medicine · 2023Article
34 more citing papers are in PubMed but not listed here.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
7 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
The Delta variant has become the dominant strain of SARS-CoV-2. We summarised the evidence on COVID-19 vaccine effectiveness (VE) identified in 17 studies that investigated VE against different endpoints. Pooled VE was 63.1% (95% confidence interval (CI): 40.9-76.9) against asymptomatic infection, 75.7% (95% CI: 69.3-80.8) against symptomatic infection and 90.9% (95% CI: 84.5-94.7) against hospitalisation. Compared with the Alpha variant, VE against mild outcomes was reduced by 10-20%, but fully maintained against severe COVID-19.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.