SynthesisBMC medicine2022
Risk factors affecting COVID-19 vaccine effectiveness identified from 290 cross-country observational studies until February 2022: a meta-analysis and meta-regression.
Synthesis in BMC medicine, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 15 papers, 2 of them syntheses that pooled it.
What it found
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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
15 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Comparative Effectiveness of mRNA-1273 and BNT162b2 COVID-19 Vaccines Among Adults with Underlying Medical Conditions: Systematic Literature Review and Pairwise Meta-Analysis Using GRADE.Advances in therapy · 2025Pooled it
- Individual risk factors associated with SARS-CoV-2 infection during Alpha variant in high-income countries: a systematic review and meta-analysis.Frontiers in public health · 2024Pooled it
- Characteristics of COVID-19 cases and factors associated with disease severity in Lao People's Democratic Republic: a nationwide study.BMC infectious diseases · 2026Observational
- Effectiveness of heterologous mRNA vaccine boosters during an Omicron wave of COVID-19: a cross-sectional study in Macao (China).Journal of thoracic disease · 2026Article
- A narrative review of heterogeneity in SARS-CoV-2 infection outcomes and vaccine efficacy: strategizing pandemic preparedness in Africa.Frontiers in public health · 2026Review
- Article
- Healthcare workers safety: a cohort study using healthcare utilisation databases on vaccination and vaccine timeliness impact against SARS-CoV-2 infection.Scientific reports · 2025Article
- Antibody levels versus vaccination status in the outcome of older adults with COVID-19.JCI insight · 2024Article
- Article
- Readiness for influenza and COVID-19 vaccination in Germany: a comparative analysis.Frontiers in psychology · 2024Article
- Vaccination status and outcomes in critical COVID-19 patients.Jornal brasileiro de pneumologia : publicacao oficial da Sociedade Brasileira de Pneumologia e Tisilogia · 2024Observational
- Anti-SARS-CoV-2 Antibody Testing: Role and Indications.Journal of clinical medicine · 2023Review
- Article
- Correlation between CD4 T-Cell Counts and Seroconversion among COVID-19 Vaccinated Patients with HIV: A Meta-Analysis.Vaccines · 2023Review
- Will Omics Biotechnologies Save Us from Future Pandemics? Lessons from COVID-19 for Vaccinomics and Adversomics.Biomedicines · 2022Review
Corrections and comments
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Authors and funding
12 authors.
Funding
Abstract
backgroundObservational studies made it possible to assess the impact of risk factors on the long-term effectiveness of mRNA and adenoviral vector (AdV) vaccines against COVID-19.
methodsA computerized literature search was undertaken using the MEDLINE, EMBASE, and MedRxiv databases to identify eligible studies, with no language restrictions, published up to 28 February 2022. Eligible were observational studies assessing vaccine effectiveness (VE) by disease severity with reference groups of unvaccinated participants or participants immunized with one, two, or three vaccine doses. Our study was carried out in compliance with the PRISMA and MOOSE guidelines. The risk of study bias was identified using the Newcastle-Ottawa Quality Assessment Scale. The GRADE guidelines were applied to assess the strength of evidence for the primary outcome. The synthesis was conducted using a meta-analysis and meta-regression.
resultsOut of a total of 14,155 publications, 290 studies were included. Early VE of full vaccination against COVID-19 of any symptomatology and severity decreased from 96% (95% CI, 95-96%) for mRNA and from 86% (95% CI, 83-89%) for AdV vaccines to 67% for both vaccine types in the last 2 months of 2021. A similar 1-year decline from 98 to 86% was found for severe COVID-19 after full immunization with mRNA, but not with AdV vaccines providing persistent 82-87% effectiveness. Variant-reduced VE was only associated with Omicron regardless of disease severity, vaccine type, or vaccination completeness. The level of protection was reduced in participants aged >65 years, with a comorbidity or those in long-term care or residential homes independently of the number of doses received. The booster effect of the third mRNA dose was unclear because incompletely restored effectiveness, regardless of disease severity, declined within a short-term interval of 4 months.
conclusionsFull vaccination provided an early high, yet waning level of protection against COVID-19 of any severity with a strong impact on the high-risk population. Moreover, the potential risk of new antigenically distinct variants should not be underestimated, and any future immunization strategy should include variant-updated vaccines.
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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.