Mask effectiveness in question with respiratory viruses

Feb. 15, 2023

A report released by the Cochrane Library 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.

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. 

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. 

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

In the review’s conclusion, Jefferson said 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. 

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 noted 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. 

Healthnews release

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