WHO: distance, face masks, and eye protection offer triple-hit protection against coronavirus

  • Chu DK & al
  • Lancet
  • 2 Jun 2020

  • curated by Liz Scherer
  • Clinical Essentials
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Takeaway

  • The triple play of physical distancing (at least 1 m), face mask, and eye protection offers the best defense against infection by SARS-CoV-2, SARS-CoV-1, and MERS-CoV viruses, WHO reports.

Why this matters

  • Public health guidance and clinicians should continue to encourage appropriate prevention precautions. 

Key results

  • Systematic review of 172 studies and a meta-analysis of 44 studies.
  • 25,697 patients with COVID-19, SARS, or MERS included.
  • Infection risk reduction with distancing: 
    • aOR: 0.18 (95% CI, 0.09-0.38). 
    • Absolute risk: 12.8% at 1 m vs 2.6% at 2 m.
    • Risk difference: −10.2% (95% CI, −11.5 to −7.5; moderate certainty).
      • Protection increased with increasing distance:
        • Risk ratio, 2.02 change/m (Pinteraction=.041).
  • Infection risk reduction with N95 or similar masks:
    • aOR: 0.15 (95% CI, 0.07-0.34). 
    • Absolute risk: 3.1% (mask) vs 17.4% (no mask).
    • Risk difference: −14.3% (95% CI, −15.9 to −10.7; low certainty).
      • Increased protection seen with N95/similar mask:
        • aOR: 0.04 (0.004-0.30) vs
        • aOR: 0.33 (0.17-0.61) other masks. 
        • Pinteraction=.090 (moderate credibility).
  • Infection risk reduction with eye protection:
    • aOR: 0.22 (95% CI, 0.12-0.39).
    • Absolute risk: 5.5% with eye protection vs 16.0% without.
    • Risk difference: −10.6% (95% CI, −12.5 to −7.7; low certainty).
    • Unadjusted risk ratio: 0.34 (95% CI, 0.22-0.52). 

Study design

  • Systematic meta-review.
  • Funding: WHO.

Limitations

  • Nonrandomized studies.
  • Recall, measurement biases.
  • Imprecise quantitative effect estimates.