Somehow the science of masks is still not settled

For many Americans, wearing a mask has become a relic. But fighting about masks, apparently not.

Masking has been widely seen as one of the best COVID precautions people can take. However, it has sparked endless arguments over mandates, what types of masks we should wear, and even how to wear them. A new review and meta-analysis of concealment studies suggests that abusers may have an opinion. The paper, a rigorous review of 78 studies, was published by Cochrane, an independent policy institution known for its reviews. The review’s authors found “little to no” evidence that population-level masking reduces COVID infections, concluding that there is “uncertainty about the effect of face masks.” That result occurred when researchers compared surgical masks to N95 masks and when they compared surgical masks to nothing.

Longtime critics of Twitter’s masking and mandates saw it as the proof they’d been waiting for. The Washington Free BeaconThe conservative newspaper quoted a researcher who called the analysis “a scientific nail for mask mandates.” Vaccine skeptic Robert Malone used it to deny what he called “self-proclaimed ‘experts'” on masking. Some researchers weighed in more nuanced comments, pointing out the limitations of the review methods that made it difficult to draw firm conclusions. Even CDC Director Rochelle Walensky pushed back on the paper in congressional testimony this week, citing its small sample size for specific COVID-19 studies. The dispute is heated and technical, and likely won’t be resolved anytime soon. But the fact that the fight continues makes it clear that there are still no firm answers to some of the most important questions about the epidemic. How effective are masks in the fight against COVID?

An important feature of Cochrane reviews is that they only look at “randomized controlled trials”, which are considered the gold standard for some types of research because they compare the effects of one intervention with another while rigorously controlling for bias and confounding variables. The trials looked at in the review compared groups of people who wore masks to those who didn’t, in an attempt to assess how effective masks were at slowing the spread of COVID in the general population. Population-level detail is important; it indicates uncertainty as to whether required all wearing a mask makes a difference in viral spread. This is different from impact individual masking that is better studied. Doctors, after all, usually wear masks when around sick patients and don’t seem to get infected any more often than anyone else. “We have pretty decent evidence that masks can protect the wearer,” Jennifer Nuzzo, an epidemiologist at Brown University, told me. “Where I think it kind of breaks down is with the population level.”

Research on individual masking generally shows what we expect. high-quality masks provide a physical barrier between the wearer and infectious particles if worn correctly. For example, one study showed that N95 masks block 57 to 90 percent of particles, depending on how well they fit. cloth and surgical masks are less effective. The caveat is that much of that support has come from laboratory studies and observational studies that don’t take into account the messiness of real life.

That the Cochrane review reasonably challenges the effectiveness of population-level masking does not mean that the results of previous studies supporting masking are inconclusive. a common theme among criticisms A limitation of the review is that it only considered a small number of studies according to Cochrane criteria; there just aren’t that many randomized controlled trials on COVID and masks. In fact, much of what is included in the review deals with masking effects other respiratory diseases, particularly influenza. Although some similarities between viruses are likely, Nuzzo clarified on TwitterTesting specific to COVID would be ideal.

The few trials in the review focusing on COVID did not provide strong support for masking. One, from Bangladesh, which looked at both cloth and surgical masks, found a 9 percent reduction in symptomatic events in the masked and unmasked groups (and a reanalysis of that study found signs of bias in the way data was collected and interpreted); Another, from Denmark, suggested that surgical masks offered no statistically significant protection at all.

Criticisms of the review argue that it might have come to a different conclusion if there had been more and better quality studies. The paper’s authors acknowledge that the trials they reviewed were prone to bias and did not control for inconsistent adherence to interventions. “Low or moderate certainty of evidence means that our confidence in the effect estimate is limited and that the true effect may differ from the observed effect estimate,” they concluded. If, after all, properly worn high-quality masks work well at the individual level, then it stands to reason that high-quality masks worn properly by many people in any given situation should indeed provide some protection.

The review’s lead author, Tom Jefferson, did not respond to a request for comment. But in a recent interview about the controversy, he weighed in on the practical implications of the new study. “There is still no evidence that masks are effective during a pandemic,” he said.

Masking all this uncertainty early in the pandemic and squaring it with mandated support is difficult. In the early days of the outbreak, evidence was scarce, Nuzzo acknowledged, but health officials had to act. Transmission was high and masking costs were low; it wasn’t immediately clear how uncomfortable and unwieldy masks can be, especially in places like schools. Mask mandates have largely expired in many places, but most people don’t mind being cautious. Nuzzo still wears a mask in a high-risk environment. “Will it prevent me from ever getting COVID? No,” he said, but it reduces his risk, and that’s good enough.

What is most disappointing about this masking uncertainty is that the pandemic has presented many opportunities for the US to collect stronger data on the effects of population-level masking, but these studies have not happened. Cloaking policies are built on sound but limited data, and when decisions are made that way, “you have to continually evaluate whether those assumptions are correct,” Nuzzo said, as NASA collects vast amounts of data to prepare for all the things that can go wrong with a shuttle launch. Unfortunately, he said, “we don’t have Houston for the pandemic.”

Achieving stronger data is still possible, though it won’t be easy. A major challenge in studying the effects of population-level masking in the real world is that people are not good at wearing masks, which of course is also an issue of mask effectiveness. It would be simple enough if you could guarantee that the participants wore their masks perfectly and consistently throughout the study. But in the real world, masks fit poorly and slide off the nose, and people generally want to take them off whenever possible.

Ideally, the research needed to gather robust data on masks and other long-standing epidemiological questions would be conducted through government. The UK, for example, has funded large randomized controlled trials of COVID drugs such as narcotics. So far, that doesn’t seem to have happened in the US. “The fact that we as a country have never really organized studies to answer the most pressing questions is a failure,” Nuzzo said. What the CDC could do is organize and fund a research network to study COVID, just as the agency has centers of excellence in areas such as food safety and tuberculosis.

The window of opportunities has not closed yet. Cochrane’s review, for all its controversies, is a reminder that more research on masking is needed, if only to examine whether anti-masking policies warrant the outrage they provoke. You’d think policymakers who encourage masking would make finding that support a priority. “If you’re going to burn your political capital, you better have some evidence to say it’s necessary,” Nuzzo said.

At this point, even the strongest possible evidence is unlikely to change the behavior of some people, given how politicized the mask debate is. But as a country, the lack of conclusive evidence leaves us ill-prepared for the next viral outbreak, COVID or otherwise. The risk is still low, but bird flu is showing worrying signs that it can be transmitted from animals to humans. If this happens, officials should tell everyone to stand up. That America has never gathered good evidence to show the population-level impact of masking for COVID, Nuzzo said, is a missed opportunity. The best time to learn more about camouflage is when we are asked to do it again.

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