Masks: meta-analysis of COVID-19 studies

Meta-analysis of masks COVID-19 studies. Only RCTs are included. Results do not rule out efficacy with specific masks and usage - for example fit-tested N95 respirators with AgCu+ZnO nanocoating or photocatalytic silver-graphene coating with thermal self-decontamination, along with strict use and appropriate replacement, decontamination, and integrity checks.
All studies   Exclusions   Cases   RCTs   Peer-reviewed   All outcomes  
Meta-analysis4 studies · 350K patientsc19early.org

Masks for COVID-19

Serious outcome risk
Masks
Control
Outcome (studies)
Improvement
Relative risk · 95% CI
All studies (4)2%
Cases (4)2%
RCTs (4)2%
Prophylaxis (4)2%
after exclusions
00.511.5+
← Masks
reduce riskIncreased
risk →
c19early.org
October 2026

Masks COVID-19 studies

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bundgaard (RCT)18%0.82 · 0.54–1.23cases42/2,39253/2,470DANMASK-19 Abaluck (RCT)9%0.91 · 0.81–0.99symp. case178,322 (n)163,861 (n) Smith (SB RCT)−98%1.98 · 0.97–4.03cases137 (n)108 (n)TRACE/STOPCOV Solberg (RCT)−7%1.07 · 0.58–1.96cases21/1,83421/1,967
Prophylaxis2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.87
All studies2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.8700.511.52+
Rotate screen for more detailsIncrease width for more details
← Masks
reduce riskMasks
increase risk →
c19early.org
October 2026

Masks COVID-19 studies after exclusions

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bundgaard (RCT)18%0.82 · 0.54–1.23cases42/2,39253/2,470DANMASK-19 Smith (SB RCT)−98%1.98 · 0.97–4.03cases137 (n)108 (n)TRACE/STOPCOV Solberg (RCT)−7%1.07 · 0.58–1.96cases21/1,83421/1,967
Prophylaxis−12%1.12 · 0.69–1.8263/4,36374/4,54512% higher risk
Tau² = 0.10, I² = 55.6%, p = 0.65
All studies−12%1.12 · 0.69–1.8263/4,36374/4,54512% higher risk
Tau² = 0.10, I² = 55.6%, p = 0.6500.511.52+
Rotate screen for more detailsIncrease width for more details
← Masks
reduce riskMasks
increase risk →
c19early.org
October 2026

Masks COVID-19 case results

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bundgaard (RCT)18%0.82 · 0.54–1.23cases42/2,39253/2,470DANMASK-19 Abaluck (RCT)9%0.91 · 0.81–0.99symp. case178,322 (n)163,861 (n) Smith (SB RCT)−98%1.98 · 0.97–4.03cases137 (n)108 (n)TRACE/STOPCOV Solberg (RCT)−7%1.07 · 0.58–1.96cases21/1,83421/1,967
Prophylaxis2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.87
All studies2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.8700.511.52+
Rotate screen for more detailsIncrease width for more details
← Masks
reduce riskMasks
increase risk →
c19early.org
October 2026

Masks COVID-19 Randomized Controlled Trials

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bundgaard (RCT)18%0.82 · 0.54–1.23cases42/2,39253/2,470DANMASK-19 Abaluck (RCT)9%0.91 · 0.81–0.99symp. case178,322 (n)163,861 (n) Smith (SB RCT)−98%1.98 · 0.97–4.03cases137 (n)108 (n)TRACE/STOPCOV Solberg (RCT)−7%1.07 · 0.58–1.96cases21/1,83421/1,967
Prophylaxis2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.87
All studies2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.8700.511.52+
Rotate screen for more detailsIncrease width for more details
← Masks
reduce riskMasks
increase risk →
c19early.org
October 2026

Masks COVID-19 peer reviewed studies

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bundgaard (RCT)18%0.82 · 0.54–1.23cases42/2,39253/2,470DANMASK-19 Abaluck (RCT)9%0.91 · 0.81–0.99symp. case178,322 (n)163,861 (n) Smith (SB RCT)−98%1.98 · 0.97–4.03cases137 (n)108 (n)TRACE/STOPCOV Solberg (RCT)−7%1.07 · 0.58–1.96cases21/1,83421/1,967
Prophylaxis2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.87
All studies2%0.98 · 0.76–1.2563/182K74/168K2% lower risk
Tau² = 0.03, I² = 41.5%, p = 0.8700.511.52+
Rotate screen for more detailsIncrease width for more details
← Masks
reduce riskMasks
increase risk →
c19early.org
October 2026

Masks COVID-19 outcomes

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bundgaard (RCT)18%0.82 · 0.54–1.23cases42/2,39253/2,470DANMASK-19 Abaluck (RCT)9%0.91 · 0.81–0.99symp. case178,322 (n)163,861 (n) Smith (SB RCT)−98%1.98 · 0.97–4.03cases137 (n)108 (n)TRACE/STOPCOV Smith (SB RCT)−58%1.58 · 0.29–8.45cases4/1372/108TRACE/STOPCOV Smith (SB RCT)−164%2.64 · 0.89–7.80misc.137 (n)108 (n)TRACE/STOPCOV Smith (SB RCT)−373%4.73 · 0.58–38.70misc.6/1371/108TRACE/STOPCOV Smith (SB RCT)−176%2.76 · 0.58–13.01misc.7/1372/108TRACE/STOPCOV Smith (SB RCT)−358%4.58 · 0.22–94.35misc.2/1370/108TRACE/STOPCOV Smith (SB RCT)69%0.31 · 0.01–7.44misc.0/1371/108TRACE/STOPCOV Solberg (RCT)−7%1.07 · 0.58–1.96cases21/1,83421/1,967
00.511.52+
Rotate screen for more detailsIncrease width for more details
← Masks
reduce riskMasks
increase risk →