Face Mask Effectiveness for Respiratory Viruses Called Into Question

During the height of the COVID-19 pandemic, facial coverings were mandatory through air travel and in different states across the U.S. Now, a new review finds question marks surrounding facial coverings for respiratory viruses like COVID-19.

Key takeaways:

A report released by the Cochrane Library on January 30, analyzes the success of physical interventions to slow down the spread of acute respiratory viruses. Findings show masks may not be as effective as previously suggested.

Different acute respiratory infections include influenza (H1N1) caused by the H1N1pdm09 virus, severe acute respiratory syndrome (SARS), and coronavirus disease 2019 (COVID‐19) caused by SARS‐CoV‐2, which was discovered in 2019.

Researchers surveyed 78 randomized controlled trials, featuring over 610,872 participants. Six of those 78 trials were from the COVID-19 pandemic — including two trials from Mexico, and one trial from Denmark, Bangladesh, England, and Norway.

Investigators also point out that much of the data was obtained during non‐epidemic influenza periods. This means much of the research occurred during a period of lower respiratory viral circulation versus COVID-19.

Studies reviewed occur in various settings, including schools, hospital wards in high-income countries, crowded urban areas in low-income countries, and immigrant populations in high-income countries.

Medical/surgical masks vs. no masks

Twelve trials surveyed compared medical/surgical masks versus no masks to prevent the spread of viral respiratory illness. Two trials occurred with healthcare workers and the remaining involved a community.

Ultimately, researchers discovered wearing medical/surgical masks has little to zero impact in preventing the spread of respiratory viruses like COVID-19 compared to those who choose not to wear masks.

N95/P2 respirators tests

In their review, researchers say the five trials analyzing N95/P2 respirators compared with medical/surgical masks on the outcome of influenza‐like illness show little findings.

In the study, lead author Tom Jefferson, and epidemiologist from the University of Oxford highlights the lack of proof in the efficiency of N95/P2 respirators versus medical/surgical masks.

"Evidence is limited by imprecision and heterogeneity for these subjective outcomes," Jefferson writes. "The use of a N95/P2 respirators compared to medical/surgical masks probably makes little or no difference for the objective and more precise outcome of laboratory‐confirmed influenza infection."

Jefferson also notes a recently concluded randomized controlled trial that found medical/surgical masks were no better than N95 respirators. The trial included 1,009 health care workers providing care to COVID-19 patients in four different countries.

In the review’s conclusion, Jefferson says the data creates question marks over the efficiency of masking. He believes well-designed, large-scale studies are needed to test the effectiveness of masks among different populations in various settings.

Clean hands vs. dirty hands

Unlike masks, hand hygiene proves to be an effective way to prevent the spread of illnesses like COVID-19. Of the 19 trials reviewed, researchers discovered a 14% drop in acute respiratory viruses in those who wash their hands.

However, Jefferson notes hand hygiene proficiency dropped when influenza‐like illness and laboratory-confirmed influenza‐like illness were compared separately. Still, the positives of hand hygiene are much more notable than those of wearing masks.

CDC on masks and hand hygiene

Although the review titled Physical Interventions to Interrupt or Reduce the Spread of Respiratory Viruses finds little evidence of masking to prevent COVID-19, the CDC still recommends facial coverings to slow the spread of the virus.

The CDC uses COVID-19 community levels to help the public be aware of the amount of COVID-19 within a specific community. If medium levels of COVID-19 are reached, the CDC says to reduce contact with high-risk friends and family, plus wearing a mask while indoors with those individuals. If COVID-19 community levels are high, the CDC says to wear a mask or respirator.


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