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Does Masking Matter? Cochrane Calls Masking Into Question

March 20, 2023

Written by Seth Walsh-Blackmore

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In this Cochrane review, hand-hygiene programs reduce the incidence of clinical acute respiratory illness (ARI), while masking probably does not provide additional benefit.

Why does this matter?
The benefits of preventive physical barriers may seem obvious, but no intervention should be assumed effective without evidence. COVID-19 revealed issues in enacting public health policy for which objective information is needed to guide future decision-making. So, what works?

Please wash your hands after pulling off your mask.
This is an update to the 2020 Cochrane review of this topic, which now only includes 78 RCTs, 6 during the COVID-19 era.

The most efficacious intervention was hand hygiene programs, with an overall RR of 0.86 (95%CI 0.81-0.90) for ARI incidence relative to control, but not for laboratory-confirmed influenza and influenza-like illness (ILI), RR 0.94 (0.81 -1.09). Hand hygiene also reduced absenteeism from work or school RR 0.64 (0.58 – 0.71) in a smaller subset of trials. One trial examined hand sanitizer vs. soap and water with RR 1.21 (1.06 – 1.39) for ARI with soap and water alone (hand sanitizer was better).

Surgical/procedure masks did not reduce the incidence of COVID/influenza-like illness relative to no masks RR 0.95 (0.84 – 1.09). N95/P2 respirators did not significantly reduce risk relative to standard masks RR 0.70 (0.45-1.10). No efficacy improvement was present for either comparison in lab-confirmed COVID/influenza.

Surface disinfection and physical distancing were reviewed, but heterogeneity precluded data pooling. No face shields, gowns, gloves, or entry point screening trials were included.

The results support continued hand hygiene as is already standard of practice. Though perhaps surprising, it supports the ongoing move away from mask mandates by many institutions. Note that most of the analyzed data are still pre-COVID-19. There are at least four RCTs awaiting publication and four active trials of physical interventions during this period, hopefully providing more robust data on masking and physical distancing.

Physical interventions to interrupt or reduce the spread of respiratory viruses. Cochrane Database Syst Rev. 2023 Jan 30;1(1):CD006207. doi: 10.1002/14651858.CD006207.pub6.

Editor’s Note: Use of masks in community settings doesn’t seem to make a big difference. This is counterintuitive and emphasizes why we need these RCTs. However, the risk reduction for individual high risk patients, with very high mask compliance, can’t be captured in a study like this. We still have a lot to learn, but this study doesn’t support general masking. ~Clay Smith

3 thoughts on “Does Masking Matter? Cochrane Calls Masking Into Question

  • This is a surprisingly simplified summary of this study. This post would have been better off to just summarize the conclusion of the authors which is much less confident than suggested by this post’s summary. I’ve never seen an article on journal feed which suggested a stronger result than the authors of the report itself.

    “The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions. There were additional RCTs during the pandemic related to physical interventions but a relative paucity given the importance of the question of masking and its relative effectiveness and the concomitant measures of mask adherence which would be highly relevant to the measurement of effectiveness, especially in the elderly and in young children. There is uncertainty about the effects of face masks. The low to moderate certainty of evidence means our confidence in the effect estimate is limited, and that the true effect may be different from the observed estimate of the effect.”

  • Thanks for this comment. You are right that there was much uncertainty and risk of bias. The authors spent many pages talking about this.

    The authors pick up where you left off above in the next sentence, “The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection.”

    The authors’ specific conclusions in the section on masking were, “Wearing masks in the community probably makes little or no difference to the outcome of influenza-like illness (ILI)/COVID-19 like illness compared to not wearing masks (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.84 to 1.09; 9 trials, 276,917 participants; moderate-certainty evidence.” And, “Wearing masks in the community probably makes little or no difference to the outcome of laboratory-confirmed influenza/SARS-CoV-2 compared to not wearing masks (RR 1.01, 95% CI 0.72 to 1.42; 6 trials, 13,919 participants; moderate-certainty evidence).”

    We (JournalFeed) said, “Masking probably does not provide additional benefit;” “[masking] doesn’t seem to make a big difference;” and, “This study doesn’t support general masking.” Those statements seem accurate based on the results of this meta-analysis. It’s hard for me to come away with a different conclusion when I read this study and look at these RRs, 95%CIs, and forest plots.
    We always provide a link to the original article so you can draw your own conclusions; you may read it differently than me. The authors concluded wearing masks in the community probably makes little to no difference. So, when I read this review, it doesn’t seem like an overstatement to say – this study does not support general masking.

    We can speculate why this may be, and the authors do. They say, “The observed lack of effect of mask wearing in interrupting the spread of influenza-like illness (ILI) or influenza/COVID-19 in our review has many potential reasons, including: poor study design; insufficiently powered studies arising from low viral circulation in some studies; lower adherence with mask wearing, especially amongst children; quality of the masks used; self-contamination of the mask by hands; lack of protection from eye exposure from respiratory droplets (allowing a route of entry of respiratory viruses into the nose via the lacrimal duct); saturation of masks with saliva from extended use (promoting virus survival in proteinaceous material); and possible risk compensation behaviour leading to an exaggerated sense of security.” But for all these reasons, and likely many more, future masking RCTs will face the same headwinds in showing a difference in meaningful outcomes.

    In the meantime, what do we do? 1) Use hand sanitizer. 2) Follow hospital mask mandates. Even though this study may not support general masking, Dr. Schmakel is absolutely right – it has inherent uncertainty, and I am not going to raise a fuss over this issue. 3) When hospital mask mandates finally go away, I think I will still wear a mask when seeing patients with active respiratory illness.

    We may not all agree on what to do with this study, and that’s OK. Some may prefer to continue wearing masks indefinitely. Please, feel free to comment.

What are your thoughts?