Soares-Weiser went on to note some limitations mentioned in the abstract of the review, including the issue of whether people in the trials actually wore masks. “Given the limitations in the primary evidence, the review is not able to address the question of whether mask-wearing itself reduces people’s risk of contracting or spreading respiratory viruses.” “It would be accurate to say that the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses, and that the results were inconclusive,” she continued. Karla Soares-Weiser, the editor-in-chief of the Cochrane Library, said in a March 10 statement. “Many commentators have claimed that a recently-updated Cochrane Review shows that ‘masks don’t work’, which is an inaccurate and misleading interpretation,” Dr. The lead author of the Cochrane review, Tom Jefferson, seemed to endorse this interpretation when he said in an interview, later quoted by conservative columnist Bret Stephens in a widely viewed opinion piece for the New York Times, “There is just no evidence that they” - referring to masks - “make any difference.”īut experts - and the Cochrane Library - say this is an inaccurate representation of what the review found. “Scientific review confirms doubters’ stance on masks and COVID-19,” declared a popular Instagram post from Fox News. “12 RESEARCH STUDIES PROVE MASKS DIDN’T WORK,” reads an Instagram post about the Cochrane review from the Liberty Counsel, a Christian religious liberty organization. So the real answer is unknown.ĭespite the limitations, many people misinterpreted the review to be saying that masks “don’t work.” In other words, there isn’t good evidence from randomized controlled trials that encouraging mask use in the community prevents the spread of respiratory diseases, but the issue also hasn’t been studied very well. “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.” “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,” the authors wrote. The authors, however, also emphasized the “uncertainty about the effects of face masks.” And only two trials in the review assessed the effectiveness of a mask intervention for COVID-19. “The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks,” the review reads. 30 review found that based on existing randomized controlled trials - which tested the effectiveness of interventions encouraging people to wear masks, rather than testing the effectiveness of masks themselves - wearing masks in the community “probably makes little or no difference” to the number of people with influenza or COVID-19-like illnesses. Reigniting the debate - and sparking misinformation about masks from both sides - is a recently released update from Cochrane, a highly-respected British nonprofit that specializes in systematic reviews of health care interventions. The evidence, however, is more complicated and nuanced - and points somewhere in between, experts told us. Some people claim masks are a panacea others say masks are worthless or worse. Three years into the COVID-19 pandemic, few topics have become as polarizing as masks. Layered, tightly woven cloth masks offer more protection, while well-fitting surgical masks and KN95 respirators provide even more protection and N95 respirators are the most protective. Loosely woven cloth masks are the least protective. The Centers for Disease Control and Prevention recommends that people wear the most protective mask that fits well and can be worn consistently. Masks should not be viewed as foolproof, as no mask is thought to offer complete protection to the wearer or to others. Observational studies, while limited, have generally found mask-wearing to be associated with a reduced risk of contracting the virus or fewer COVID-19 cases in a community.Ī few randomized controlled trials have found that providing free masks and encouraging people to wear them results in a small to moderate reduction in transmission, although these results have not always been statistically significant. Lab tests, for example, show that certain masks and N95 respirators can partially block exhaled respiratory droplets or aerosols, which are thought to be the primary ways the virus spreads. Multiple lines of evidence back the use of face masks to protect against the coronavirus, although some uncertainty remains as to how effective mask interventions are in preventing spread in the community.
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