Masks During Pandemics Caused by Respiratory Pathogens—Evidence and Implications for Action

The study “Masks During Pandemics Caused by Respiratory Pathogens—Evidence and Implications for Action” by Shama Cash-Goldwasser and colleagues provides a comprehensive overview of the role of face masks in controlling the spread of respiratory pathogens, particularly in the context of the COVID-19 pandemic.

Here is a detailed summary:


  • The study emphasizes the importance of face masks in reducing the spread of respiratory viruses like influenza and SARS-CoV-2, which have caused deadly pandemics.
  • Despite the controversial nature of mask use in community settings, it remains a critical public health tool, and understanding its efficacy is vital for future pandemic responses​​.

Key Observations

  • Observational studies have consistently demonstrated that mask use in community settings is associated with reduced transmission of SARS-CoV-2.
  • The study highlights that disagreements about mask efficacy often arise from a focus on randomized clinical trials (RCTs), which have limitations in scope and power for assessing public health interventions like mask usage.
  • The evidence supporting mask use is robust and comes from diverse settings and populations, indicating that masks should be a key component of responses to respiratory epidemics and pandemics​​.

Randomized Clinical Trials on Masking

  • Two significant RCTs conducted during the pandemic offer insights:
    1. A Danish study with inconclusive results due to insufficient sample size.
    2. A larger study in Bangladesh showed a statistically significant reduction in symptomatic SARS-CoV-2 infections in communities practicing widespread masking.
  • These studies indicate that while RCTs are informative, they are not the sole source of evidence for public health policies​​.

Observational Studies

  • Prior to COVID-19, studies on SARS and MERS showed that mask use significantly reduced infection risks.
  • During the pandemic, various observational studies have reinforced the effectiveness of masks, showing that they reduce the spread of potentially infectious respiratory droplets and aerosols.
  • The type and fit of the mask significantly influence its efficacy, with N95 respirators showing higher filtration efficiency than surgical masks.
  • Observational studies have also demonstrated mask effectiveness in various settings, such as airplanes, schools, and households​​.


  • Mask effectiveness depends on several factors, and no public health intervention is 100% effective.
  • The best masks provide substantial protection, but their effectiveness is limited if they are not used consistently across all settings where transmission occurs.
  • The study concludes that masking, as part of a layered public health response including vaccination and isolation of infectious people, is crucial in controlling pandemics caused by respiratory pathogens.
  • Decision-makers should rely on existing and rapidly generated evidence, including observational studies, rather than solely on RCTs and meta-analyses, for public health decisions.
  • The study underscores that high-quality masks should play a crucial role in controlling future pandemics caused by respiratory pathogens​​.

Overall, the study by Cash-Goldwasser et al. provides strong evidence for the effectiveness of masks in reducing the spread of respiratory viruses, with implications for future pandemic preparedness and response strategies.

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