#18,205
Although we've seen ample evidence that the consistent wearing of surgical masks and/or N95 respirators in high risk areas (crowds, poorly ventilated indoor spaces, etc.) can significantly reduce the risk of respiratory infection, there remains a high level of resistance to donning them.
I live in what would be described as a `retirement' community, but I rarely see anyone wearing a mask in public (unless I'm looking in a mirror).
Masks are admittedly inconvenient, and can be uncomfortable (particularly in the summer), but at my age (> 70) I consider wearing them far less onerous than a week in bed with COVID, or worse, being hospitalized.
Others may look at their individual risks, and come to a different conclusion.
Unfortunately, the internet is filled with memes declaring that `Masks don't work', erroneously citing a 2023 Cochrane study in order to prove their point.
In March of last year Karla Soares-Weiser, Editor-in-Chief of the Cochrane Library, issued a statement (see Cochrane Statement On Misinterpretations Of Their Mask Study) clarifying the study's findings.
But memes are no slave to facts, and so people continue to post (and believe) them.
With COVID rising once again and the fall respiratory season not far off, people will once again need to evaluate the risks and rewards of wearing a mask in public.
Today we've a new clinical trial that finds that wearing even a surgical mask in public can reduce the risks of respiratory infection. While the impact was modest (a 29% reduction in symptomatic infections), it is a relatively simple and low-cost intervention.
I've reproduced the abstract and summary below, but you'll want to follow the link to read the report (and its limitations) in its entirety. I'll have a postscript after the break.
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Research
Personal protective effect of wearing surgical face masks in public spaces on self-reported respiratory symptoms in adults: pragmatic randomised superiority trial
BMJ 2024; 386 doi: https://doi.org/10.1136/bmj-2023-078918 (Published 24 July 2024)
Cite this as: BMJ 2024;386:e078918
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Peer review
Runar Barstad Solberg, scientist1,Atle Fretheim, professor and research director12, Ingeborg Hess Elgersma, scientist1, Mette Fagernes, senior adviser3, Bjørn Gunnar Iversen, senior medical officer3, Lars G Hemkens, senior scientist456, Christopher James Rose, statistician17, Petter Elstrøm, senior scientist1Author affiliations
Correspondence to: R B Solberg runar.solberg@fhi.no (or @Runar_Solberg on X)Accepted 29 May 2024
Abstract
Objective To evaluate the personal protective effects of wearing versus not wearing surgical face masks in public spaces on self-reported respiratory symptoms over a 14 day period.
Design Pragmatic randomised superiority trial.
Setting Norway.
Participants 4647 adults aged ≥18 years: 2371 were assigned to the intervention arm and 2276 to the control arm.
Interventions Participants in the intervention arm were assigned to wear a surgical face mask in public spaces (eg, shopping centres, streets, public transport) over a 14 day period (mask wearing at home or work was not mentioned). Participants in the control arm were assigned to not wear a surgical face mask in public places.
Main outcome measures The primary outcome was self-reported respiratory symptoms consistent with a respiratory infection. Secondary outcomes included self-reported and registered covid-19 infection.
Results Between 10 February 2023 and 27 April 2023, 4647 participants were randomised of whom 4575 (2788 women (60.9%); mean age 51.0 (standard deviation 15.0) years) were included in the intention-to-treat analysis: 2313 (50.6%) in the intervention arm and 2262 (49.4%) in the control arm. 163 events (8.9%) of self-reported symptoms consistent with respiratory infection were reported in the intervention arm and 239 (12.2%) in the control arm.
The marginal odds ratio was 0.71 (95% confidence interval (CI) 0.58 to 0.87; P=0.001) favouring the face mask intervention. The absolute risk difference was −3.2% (95% CI −5.2% to −1.3%; P<0.001). No statistically significant effect was found on self- reported (marginal odds ratio 1.07, 95% CI 0.58 to 1.98; P=0.82) or registered covid-19 infection (effect estimate and 95% CI not estimable owing to lack of events in the intervention arm).
Conclusion Wearing a surgical face mask in public spaces over 14 days reduces the risk of self-reported symptoms consistent with a respiratory infection, compared with not wearing a surgical face mask.
Trial registration ClinicalTrials.gov NCT05690516.
(SNIP)
Conclusion
Wearing surgical face masks is superior to not wearing surgical face masks in reducing the risk of respiratory symptoms over 14 days. The effect size was moderate, but wearing a face mask is a simple intervention with low burden and of relatively low cost and is one of several public health and social measures that may be worth considering for reducing the spread of respiratory infections.
What is already known on this topic
- The effectiveness of face masks as a protective measure against infection is uncertain
- Observational studies suggest that face masks reduce the risk of respiratory tract infections
What this study adds
- (and its limitations)Findings from randomised trials are, however, highly uncertain owing to methodological limitations such as insufficient statistical power
- Our pragmatic trial provides evidence that wearing surgical face masks in public spaces reduces the incidence of self-reported respiratory symptoms consistent with respiratory infections in real world settings
- Unlike most earlier trials of face mask, our study was sufficiently powered
- Similar trials can and should be conducted for other public health and social measures
While I personally would opt for a KN95/N95 mask over a surgical mask (assuming I had the choice), a nearly 30% reduction in illness is nothing to sneeze at.
