SynthesisJornal brasileiro de pneumologia : publicacao oficial da Sociedade Brasileira de Pneumologia e Tisilogia2024
Effectiveness of wearing masks during the COVID-19 outbreak in cohort and case-control studies: a systematic review and meta-analysis.
Synthesis in Jornal brasileiro de pneumologia : publicacao oficial da Sociedade Brasileira de Pneumologia e Tisilogia, 2024. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 5 papers, 1 of them a synthesis 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
5 citing papers in PubMed, 1 synthesis or guideline pooled it, 6 citations in OpenAlex.
- Evidence of Face Masks and Masking Policies for the Prevention of SARS-CoV-2 Transmission and COVID-19 in Real-World Settings: A Systematic Literature Review.International journal of environmental research and public health · 2025Pooled it
- Effects of Green Tea Gargling on COVID-19: A Multicenter RCT.AJPM focus · 2026Article
- Synthesis challenges in complex evidence: A critical analysis of systematic reviews of face mask efficacy.Research synthesis methods · 2026Article
- COVID-19-associated neurological and psychological manifestations.Nature reviews. Disease primers · 2025Review
- Comparative Assessment of Viral Load Retention in Surgical and Fabric Masks Worn by COVID-19 Patients.Viruses · 2025Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
6 authors at 4 institutions in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectiveTo evaluate the efficacy of wearing a mask to prevent COVID-19 infection.
methodsThis was a systematic review and meta-analysis of cohort and case-control studies, considering the best level of evidence available. Electronic databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Clinical Trials.gov) were searched to identify studies that evaluated the effectiveness of wearing masks compared with that of not wearing them during the COVID-19 pandemic. Risk of bias and quality of evidence were assessed using the Cochrane risk of bias tool and the Grading of Recommendations Assessment, Development, and Evaluation.
resultsOf the 1,028 studies identified, 9 met the inclusion criteria (2 cohort studies and 7 case-control studies) and were included in the analysis. The meta-analysis using cohort studies alone showed statistically significant differences, wearing a cloth mask decreased by 21% [RD = -0.21 (95% CI, -0.34 to -0.07); I2 = 0%; p = 0,002] the risk of COVID-19 infection, but the quality of evidence was low. Regarding case-control studies, wearing a surgical mask reduced the chance of COVID-19 infection [OR = 0.51 (95% CI, 0.37-0.70); I2 = 47%; p = 0.0001], as did wearing an N95 respirator mask [OR = 0.31 (95% CI, 0.20-0.49); I2 = 0%; p = 0.00001], both with low quality of evidence.
conclusionsIn this systematic review with meta-analysis, we showed the effectiveness of wearing masks in the prevention of SARS-CoV-2 infection regardless of the type of mask (disposable surgical mask, common masks, including cloth masks, or N95 respirators), although the studies evaluated presented with low quality of evidence and important biases.
Indexed as
Identifiers
What OpenQuestion holds
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.