Are Face Masks Effective? The Evidence.
swprs.org
Updated: July 2022
Published: July 2020
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An overview of the current evidence regarding the effectiveness of face masks.
Contents A) Studies ? B) WHO review ? C) Real-world evidence ? D) N95/FFP2 masks ? E) Additional aspects ? F) The aerosol issue ? G) Contrary evidence ? H) Mask-related risks ? I) Conclusion ?
A) Studies on the effectiveness of face masks So far, most studies found little to no evidence for the effectiveness of face masks in the general population, neither as personal protective equipment nor as a source control.
- A May 2020 meta-study on pandemic influenza published by the US CDC found that face masks had no effect, neither as personal protective equipment nor as a source control. ( Source)
- A WHO review of ten randomized controlled trials of face masks against influenza-like illness, published in September 2019, found no statistically significant benefit. ( Source)
- A Danish randomized controlled trial with 6000 participants, published in the Annals of Internal Medicine in November 2020, found no statistically significant effect of high-quality medical face masks against SARS-CoV-2 infection in a community setting. ( Source)
- A large randomized controlled trial with close to 8000 participants, published in October 2020 in PLOS One, found that face masks “did not seem to be effective against laboratory-confirmed viral respiratory infections nor against clinical respiratory infection.” ( Source)
- A February 2021 review by the European CDC found no high-quality evidence in favor of face masks and recommended their use only based on the ‘precautionary principle’. ( Source)
- A July 2020 review by the Oxford Centre for Evidence-Based Medicine found that there is no evidence for the effectiveness of face masks against virus infection or transmission. ( Source)
- A November 2020 Cochrane review found that face masks did not reduce influenza-like illness (ILI) cases, neither in the general population nor in health care workers. ( Source)
- An August 2021 study published in the Int. Research Journal of Public Health found “no association between mask mandates or use and reduced COVID-19 spread in US states.” ( Source)
- An experimental study using virus aerosols, published in May 2022 in the Journal of Infectious Diseases, found that only professionally fit-tested N95/FFP2 masks, but not surgical masks or non-fitted N95/FFP2 masks, reduced viral loads in nostrils. ( Source)
- A large Spanish school study, published in March 2022, found that “mask mandates in schools were not associated with lower SARS-CoV-2 incidence or transmission.” ( Source)
- A May 2020 article by researchers from Harvard Medical School, published in the New England Journal of Medicine, concluded that face masks offer “little, if any, protection”. ( Source)
- A 2015 study in the British Medical Journal BMJ Open found that cloth masks were penetrated by 97% of particles and may increase infection risk by retaining moisture or repeated use. ( Source)
For a review of studies claiming face masks are effective, see section G) below. |
