Several reviews found that there is no significant reduction in the transmission of respiratory infections in randomized controlled trials. 

Limited Evidence of Effectiveness

Individuals may feel as though wearing face masks provide a sense of security that allows them to disregard other important hygienic practices such as washing their hands or physical distancing.

False Sense of Security

Government officials and some health officials advise against the use of face masks citing concerns regarding the limited quantities of face masks in circulations, meant for health workers in hospitals, nursing homes, and other congregate facilities as well as at-risk individuals.

Limited Quantities

Many sources point out that members of the public may not wear face masks in its intended usage, such as leaving the nose uncovered, taking off the mask whenever it feels uncomfortable, or reusing disposable masks.

Improper or Inconsistent Usage of Face Masks Among Community Members 

- Limited Evidence of Effectiveness
- Improper or Inconsistent Usage
- False Sense of Security
- Limited Quantities

University of California, Davis

Face masks are thought to reduce or prevent transmission of the viral particles through aerosol transmission. The usage of face masks is a controversial topic whose efficacy is disputed by governments, researchers, and the public. Health officials in the early stages of the pandemic advised against the use of face masks for various reasons, although recent developments in the area of research may influence their perspectives.

Face Masks to Prevent the Spread of COVID-19

Greenhalgh, T., Schmid, M. B., Czypionka, T., Bassler, D., & Gruer, L. (2020). Face masks for the public during the covid-19 crisis. Bmj, 369.
https://doi.org/10.1136/bmj.m1435

Face masks for the public during the covid-19 crisis

Arguments Against the Use of Face Masks

- Use as a Precautionary Measure
- Blocking of Aerosol Agents
- Reduce Transmission from Asymptotic Individuals

Arguments Supporting the Use of Face Masks

Types of Face Masks

- Model simulations created using data from New York and Washington suggests that even less effective masks have large implications in decreasing transmission rates of COVID-19.
- The greatest advantages are conferred when face masks are used in conjunction with other countermeasures such as physical distancing, sanitation, and personal hygiene. Nation-wide adoption, and high compliance rates are key to limiting the spread of the virus.

Compartmental Model Assessing Community-Wide Usage of Face Mask

- The BMJ
- WHO
- The New England Journal of Medicine (NEJM)
- Le Infezioni in Medicina
- Infectious Disease Modeling
- BioRxiv
- JAMA

References for Face Masks and COVID-19  by Source/Journal

8 face masks were tested using polydisperse indoor air. Their effectiveness was examined for aerosol of aerodynamic diameters of 0.006 μm to 10 μm. The commercially available masks used in this study were:
- Five were 3-layer mask (labeled M1, M2, M3, M4, and M5 in the study)
- One was a KN95 mask with one-way valve (labeled M6 in the study)
- Two were fabric masks (labeled F1- simple cloth mask, and F2- cloth mask with activated carbon)

Aerosol filtering efficiency of respiratory face masks used during the COVID-19 pandemic. 

Studies demonstrating increases or decreases in COVID-19 transmission due to masking or masklessness.

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