Somehow, the science on masks still isn’t settled

For many Americans, mask-wearing has become a munition. but fighting About masks, it seems, did not.

Masking is widely seen as one of the best COVID precautions people can take. Yet it has sparked an ongoing debate: about mandates, what kinds of masks we should wear, and even how to wear them. A new review and meta-analysis of masking studies suggests detractors may have a point. The paper — a rigorous evaluation of 78 studies — was published by Cochrane, an independent policy institute best known for its reviews. The review’s authors found “little or no” evidence that masking at the population level reduces COVID infection, and concluded that there is “uncertainty about the effects of face masks.” This result was obtained when researchers compared surgical masks to N95 masks, and when they compared surgical masks to none.

On Twitter, longtime critics of Stealth and Delegations have deemed this the clue they have been waiting for. Washington Free Lighthouse, a conservative outlet, quoted a researcher who called the analysis “the scientific nail in the coffin of mask mandates.” Vaccine skeptic Robert Mallon used it to refute what he called “self-appointed” “experts” on disguises. Some researchers weigh in with more accurate interpretations, noting limitations in review methods that made it difficult to draw firm conclusions. Even CDC Director Rochelle Walensky disputed the paper in congressional testimony this week, pointing to the small sample size of studies on COVID. The debate is hot and technical, and probably won’t be resolved anytime soon. But the fact that the battle is on shows that there is still no definitive answer to the pandemic’s most important questions: How effective are masks at stopping COVID?

An important feature of Cochrane reviews is that they look only at ‘randomized controlled trials’, which are considered the gold standard for certain types of research because they compare the effect of one intervention to another while tightly controlling for biases and confounding variables. The trials considered in the review compared groups of masked people with those who did not attempt to estimate the effectiveness of masking in reducing the spread of COVID in the general population. Detail at the population level is important: it indicates uncertainty about whether or not it is required everyone Wearing a mask makes a difference in spreading the virus. This is different from effect Individually Hide, which is better researched. After all, doctors routinely mask when they’re around patients and never seem to get sick any more than anyone else. “We have fairly decent evidence that masks can protect wearers,” Jennifer Nuzzo, an epidemiologist at Brown University, told me. “Where I think it kind of breaks down has to do with relating that to the population level.”

Individual mask research generally shows what we expected: High-quality masks provide a physical barrier between the wearer and infectious particles, if worn properly. For example, in one study, N95 masks were shown to block 57 to 90 percent of particles, depending on their fit; Cloth and surgical masks are less effective. The caveat is that much of this support has come from laboratory research and observational studies, which don’t explain real-life clutter.

That a Cochrane review reasonably challenges the efficacy of masking at the population level does not mean that the findings of previous studies in support of masking are moot. a common theme among the criticisms From the review it considered only a small number of studies according to the Cochrane criteria; There aren’t a lot of randomized controlled trials on COVID and masks. In fact, most of the people included in the review are all about the masking effect last Respiratory disease, which is influenza. Although there may be some similarities between viruses, Nuzzo explained on TwitterCOVID-specific experiences would be ideal.

The few trials in the COVID-focused review do not show strong support for masking. One of them, from Bangladesh, which looked at both cloth and surgical masks, found a 9 percent reduction in incidence of symptoms in the masked versus unmasked groups (and a re-analysis of that study found signs of bias in the way the data was collected and interpreted); Another, from Denmark, suggested that surgical masks provide no statistically significant protection at all.

Criticisms of the review suggest that it might have reached a different conclusion if more and better quality studies had become available. The paper’s authors acknowledge that the trials they considered were subject to bias and did not control for inconsistent adherence to the interventions. They concluded, “The low to medium certainty of the evidence means that our confidence in the effect estimate is limited, and that the true effect may differ from the observed estimate of effect.” If high-quality masks that are worn work well on an individual level, then it stands to reason that high-quality masks worn correctly by many people in any situation should already provide some level of protection.

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

It is difficult to iron out all this uncertainty while supporting masking and mandates early in the pandemic. Nozo acknowledged that evidence of this was scarce in the early days of the pandemic, but that health officials had to act. Transmission was high, and masking costs were considered low; It wasn’t immediately clear how uncomfortable and unmanageable masks can be, especially in settings like schools. Mask mandates are pretty much expired in most places, but it never hurts most people to err on the side of caution. Nuzzo still wears a mask in high-risk environments. “Will it prevent me from getting COVID at all?” No, she said, but it reduces the risk — and that’s good enough.

What’s most frustrating about this masking of uncertainty is that the pandemic has provided many opportunities for the United States to collect stronger data on the effects of masking at the population level, but these studies haven’t happened. Masking policies are made based on sound but limited data, and when decisions are made in this way, Nuzzo said “you need to constantly evaluate whether those assumptions are correct” — much like the way NASA gathers massive amounts of data to prepare for all the things it does. Something could go wrong with the shuttle launch. Unfortunately, she said, “We don’t have Houston for a pandemic.”

Stronger data is still possible, though it won’t be easy. One of the main challenges of studying the effect of masking at the population level in the real world is that people are not very good at wearing masks, and this of course presents a problem with the effectiveness of masks as well. It would be easy enough to ensure that participants wore their masks perfectly and consistently throughout the study. But in the real world, masks fit poorly and slip off their noses, and people are generally anxious to take them off whenever possible.

Ideally, the research needed to gather solid data — about masks, and other lingering epidemiological questions — would be done through government. The UK, for example, has funded large randomized controlled trials of COVID drugs such as molnopivir. So far, this does not appear to have occurred in the United States. None of the new studies on masking included in the Cochrane Review were funded by the US government. “The fact that we as a country have never done studies to answer the most pressing questions is a failure,” Nozzo said. What the CDC could do is organize and fund a research network to study COVID, like the agency’s centers of excellence in areas like food safety and tuberculosis.

The window of opportunity has not closed yet. The Cochrane review, for all its controversy, is a reminder that more research on masking is needed, if only to address whether pro-masking policies warrant the outrage they incite. You would think that policymakers who encouraged masking would make finding such support a priority. “If you’re going to burn your political capital, it would be nice to have the evidence to say it’s necessary,” Nozzo said.

At this point, even the strongest possible evidence is unlikely to change some people’s behavior, given how politicized the mask debate is. But as a country, the lack of hard evidence leaves us ill-prepared for the next viral outbreak — COVID or otherwise. The risk remains low, but bird flu is showing worrying signs that it can jump from animals to people. If that happens, should the officials require everyone to disguise themselves? Because America has never gathered good evidence to show the effect of masking the population level of COVID, Nuzzo said, it was a missed opportunity. The best time to learn about masking is before we are asked to do it again.


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