Cochrane Says Review Does Not Show That ‘Face Masks Don’t Work’ Against Covid-19

You know that recently published Cochrane review that some have claimed as evidence that face masks don’t work? Well, have some of these claims been a bit, shall we say, too cocky and not Cochrane-y enough? Well, in a statement issued on March 10 by the Cochrane Library, Karla Soares-Weiser, Editor-in-Chief of the Cochrane Library, emphasized, “Many commentators have claimed that a recently-updated Cochrane Review shows that ‘masks don’t work,’ which is an inaccurate and misleading interpretation.” Yikes.

Soares-Weiser didn’t specify in the statement who exactly those “commentators” were. But she could have been referring to Brett Stephens, who wrote a February 21, 2023, Opinion piece for The New York Times entitled, “The Mask Mandates Did Nothing. Will Any Lessons Be Learned.” Or maybe she was referring to Tom Jefferson, the Cochrane review’s first author, a Senior Associate Tutor at the Department for Continuing Education at the University of Oxford, and notably an Author for The Brownstone Institute. Stephens quoted Jefferson as saying the following about face masks, “There is just no evidence that they make any difference. Full stop.” That’s presumably based on Jefferson’s based on the systematic review of face mask studies that he and his team conducted and published in the Cochrane Library on January 30. Well, looks like such statements didn’t really accurately represent what the systematic review found, full stop. And now the Cochrane Library is essentially saying, full stop it with all such misleading interpretations.

In fact, Soares-Weiser’s statement went on to delineate what the systematic review can and can’t do and what claims ultimately may be doo-do0: “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. 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.”

A number of scientists and public health experts have already emphasized the various flaws of the systematic review conducted by Jefferson and his team. For example, Lucky Tran, PhD, an organizer for the March for Science and a science communicator at Columbia University, wrote in an Opinion piece for The Guardian entitled, “Don’t believe those who claim science proves masks don’t work,” that “The analysis [by Jefferson and his team] is flawed because it compares apples to oranges.” The systematic review didn’t compare actual apples with actual oranges, which has already been done before and has shown that you should really peel oranges before eating them. Rather, what Tran meant is that “The paper mixes together studies that were conducted in different environments with different transmission risks. It also combines studies where masks were worn part of the time with studies where masks are worn all the time. And it blends studies that looked at Covid-19 with studies that looked at influenza.”

That’s a whole lot of mixing going on and makes you wonder why the authors of the review didn’t instead separate out the studies. After all, as Tran emphasized in his Opinion piece, “If apples work and oranges don’t, but your analysis mixes them together, you may come to the false conclusion that apples don’t work. Out of the 78 papers analyzed in the review, only two actually studied masking during the Covid-19 pandemic. And both of those found that masks did protect wearers from Covid-19.”

Yeah mixing Covid-19 studies and flu studies would be sort of like mixing orange spray tan with an Apple computer. Things could get very messy. Remember Covid-19 ain’t the flu. it just ain’t. While both are respiratory viruses, the flu virus can’t float around in the air nearly as well as the Covid-19 coronavirus, otherwise known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoVC-2), can. Early on in 2020, authorities thought that the SARS-CoV-2 behaved more like the flu virus in the air. The thinking was that like the flu virus the SARS-CoV-2 was carried primarily by large respiratory droplets that would travel no further than six feet due to that thing called gravity. That was the rationale for the initial stay six feet (or one Gosling because Ryan Gosling is about six feet tall) apart from one another.

However, a pandemic game changer was when studies revealed that the SARS-CoV-2 could actually travel in smaller and lighter respiratory droplets that could hang in the air for much longer periods of time and could float for more than six feet. This game changing finding that the SARS-CoV-2 can go all aerosol is what prompted the change in face mask guidance in the Spring of 2020. Therefore, including so many studies focused on the flu virus rather than the SARS-CoV-2, in the words of Tran, “drowned out” the SARS-CoV-2 “by the greater number of studies on influenza included, where the benefit of masking is harder to detect because it’s a far less contagious virus than Covid-19.”

Tran brought in another piece of fruit into the mix by calling the Cochrane review “a classic example of cherry-picking, where biased groups highlight a subset of data that support their position, while ignoring the larger pool of evidence that disagrees with them.” Tran went on to point out that “Many direct studies in labs show that high-quality masks significantly reduce the number of viral particles mask-wearers inhale and emit, but these are intentionally omitted in the arguments of anti-maskers.” I’ve also described for Forbes other scientific studies that have supported the use of face masks, studies that were omitted by Jefferson’s Cochrane review. Moreover, if face masks don’t work, why did the spread of respiratory viruses plummet during the Winters of 2020-2021 and 2021-2022 when, guess what, face masks were being used more widely? Life may be a bowl of cherries, but cherry picking only certain studies to support a viewpoint would be the “pits.”

Hmm, why might have Jefferson and his team have “cherry picked” certain studies? Could an A-word have been involved? No, not that A-word. Rather, the A-word as in “agenda.” Well, Gavin Yamey, MD, MPH, MA, the Hymowitz Professor of Global Health and a Professor of Public Policy at Duke University, tweeted out that the Jefferson works with the Brownstone Institute and that “Brownstone has always been an extremely anti-mask, anti-vaxx right wing think tank”:

In fact, a closer look at the Cochrane Library publication shows that even the authors admitted that their review is very limited. This was emphasized by Soares-Weiser’s statement that read, “The review authors are clear on the limitations in the abstract: ‘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.’” Soares-Weiser’s statement continued by saying, “Adherence in this context refers to the number of people who actually wore the provided masks when encouraged to do so as part of the intervention. For example, in the most heavily-weighted trial of interventions to promote community mask wearing, 42.3% of people in the intervention arm wore masks compared to 13.3% of those in the control arm.” Less than 50% adherence is not great adherence. So when less than half of people are adhering to an intervention, is the intervention really in place?

Nevertheless, these stated limitations didn’t full stop Jefferson from saying that “full stop” quote in an interview. They haven’t stopped various political leaders, TV personalities, and anonymous social media accounts either from further amplifying Jefferson’s Cochrane publication to keep pushing the narrative that face masks somehow don’t work. Will these same people be as zealous at amplifying Soares-Weiser’s statement about the limitations of Jefferson’s Cochrane publication? Don’t hold your breath for this to happen.

One challenge throughout the Covid-19 pandemic has been people employing the political tactic of using vague language to suggest something without coming right out and saying it. This is a bit like saying, “I love your new outfit, I wish I had one like that but I think I’m too skinny for that style.” An even closer look at Jefferson’s Cochrane review reveals some questionable language. As Soares-Weiser’s statement mentioned, “The original Plain Language Summary for this review stated that ‘We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses based on the studies we assessed.’” Such a statement may sound a little more passive-aggressive than science-y. Indeed, Soares-Weiser’s statement admitted that “This wording was open to misinterpretation, for which we apologize.” She added, “While scientific evidence is never immune to misinterpretation, we take responsibility for not making the wording clearer from the outset.” Soares-Weiser indicated that “We are engaging with the review authors with the aim of updating the Plain Language Summary and abstract to make clear that the review looked at whether interventions to promote mask wearing help to slow the spread of respiratory viruses.”

This is reminder that you should never use a single scientific publication to draw a conclusion. Instead, it’s important to look at what studies say as a whole. Some have claimed that publications in the Cochrane Library should always serve as “gold standards.” For example, Vinayak Prasad, MD, MPH, a Professor of Epidemiology & Biostatistics at the University of California, San Francisco, whose work prior to the pandemic has been mainly in oncology and not infectious diseases, called Jefferson’s Cochrane review a “gold standard for mask studies” in a tweet. A Cochrane review may serve as a “gold standard” to some degree when evaluating a bunch of randomized controlled trials (RCTs) that evaluate a single medication under very controlled and similar circumstances such as a cancer medication that’s being administered and monitored by doctors from a hospital or clinic.

But such claims about Cochrane reviews and RCTs are more like “fool’s gold” when it comes to other types of scientific questions. It’s important to remember that face mask use is a population-based intervention and not simply an individual-based intervention. The effectiveness of a face mask does depend not only on what kind of face mask you are wearing and how you wear it but also how many people around you are wearing face masks.

It’s time to face mask the facts. Many people have politicized the heck out of face masks to the point that they are not even acknowledging what scientific studies prior to the Cochrane review have shown. Instead, they’ve been doing a lot of cherry-picking, selecting bits and pieces of things here and there to support their narrative. Heck, even a Cochrane Library publication can be used in a cockeyed manner.