- A review study from a British health research group shows community masking probably made little difference in curbing COVID
- But defenders of government masking policies note some limitations in the Cochrane study and argue that proper masking still has utility
- Experts say more and better masking studies are needed
Were mask mandates and guidance put in place during the pandemic effective in reducing the spread of COVID-19?
That question has divided people in Michigan and around the country almost from the start of the pandemic in early 2020. Most mask mandates have ended at least for now, though the Centers for Disease Control and Prevention (CDC) and other public health authorities, including the Michigan Department of Health and Human Services, continue to recommend masking to reduce the spread of COVID-19 in certain circumstances.
But recently, a broad review of studies by Cochrane, a respected international health research group, concluded that masking in the community “probably makes little or no difference” in slowing the spread of respiratory illnesses such as the flu or COVID-19 “compared to not wearing masks.” That was likely true, the study found, whether those wearing masks used ordinary surgical masks or higher-quality N95 masks.
The findings were celebrated as long-sought validation among the many, diverse critics of mask mandates, even as mainstream U.S. health experts were quick to highlight what they saw as key limitations of the analysis, including that few of the studies Cochrane analyzed were specific to COVID-19.
Within the latter group is Dr. Natasha Bagdasarian, chief medical executive for the state of Michigan, who noted to Bridge Michigan the findings are not new but rather a collection of results from prior studies. The analysis goes into our knowledge base, she said, “but it has to be taken in the context of everything else.”
“There’s a lot of good data out there that supports masking,” Bagdasarian said, particularly in settings such as hospitals where masking has been successful and protective for decades.
A review of studies
Cochrane researchers reviewed 78 randomized controlled trials of masking and other mitigation strategies used to curb the spread of respiratory illnesses. Randomized controlled trials, or RCTs, are considered the gold standard of studies because they allow researchers to more rigorously isolate cause-and-effect relationships between an intervention — masking, for example — and an outcome, such as reduced spread of COVID-19.
The randomized controlled trials examined in the review — which included six conducted during the pandemic — involved more than 600,000 participants from many countries. Twelve of the trials specifically compared the use of medical and surgical masks to not wearing masks.
Cochrane’s focus: Whether certain physical measures stop or slow transmission of respiratory viruses?
The answer, regarding masking at least, was largely, no; masking had little to no impact on curtailing the spread of infection in the community. While hand washing was likely to “modestly reduce the burden of respiratory illness.”
Dr. Vinay Prasad, a professor of epidemiology and a hematologist-oncologist at the University of California San Francisco, who attended Michigan State University as an undergraduate, said in a YouTube video the review’s major takeaway was that for influenza- or COVID-like illnesses, masks had “maybe at best a mild effect, but most likely no effect at all.”
“We’ve not proven that there is an effect, let me put it that way,” he said.
Lead Cochrane review author Tom Jefferson, an epidemiologist and senior associate tutor at the University of Oxford, had a similar take, telling Australian journalist Maryanne Demasi the evidence hadn’t changed much since an earlier Cochrane study in 2020. “There’s still no evidence that masks are effective during a pandemic,” he said.
Mike Shirkey, the former Senate majority leader, was part of a group of state Republican lawmakers who sued Gov. Gretchen Whitmer over her aggressive use of emergency powers during the first year of the pandemic.
He told Bridge it shouldn’t have taken the latest Cochrane review to convince public officials of the futility of mask mandates.
Other than some “very high-tech” surgical masks, he said, “it was ridiculous to even require them.”
Findings draw broad criticism
There was pushback to the Cochrane findings even as health officials were careful to acknowledge the British nonprofit’s sterling reputation for analyzing healthcare data.
Defenders of the continued utility of masking against COVID-19 noted two important limitations of the findings, which Cochrane also acknowledged.
First, they argued, the findings focused on mask rules at the population level, and should not be read to mean that masks, when properly and consistently worn, are not effective for individuals, as numerous studies have previously found, particularly in environments like health care facilities.
“We have fairly decent evidence that masks can protect the wearer,” Jennifer Nuzzo, an epidemiologist at Brown University, told The Atlantic. “Where I think it sort of falls apart is relating that to the population level.”
The second argument some experts have made is that the problem isn’t mask mandates themselves; the problem is that a good chunk of the population isn’t going to follow them, much less properly and consistently wear masks.
Cochrane acknowledged that limitation, noting that “relatively low adherence with the interventions during the studies hampers drawing firm conclusions,” and the “results might change when further evidence becomes available.”
Dr. Bagdasarian noted Cochrane did not include “real world” or observational studies looking at what actually happened in communities where people were masking. While she noted RCTs are the gold-standard for evidenced-based medicine, she said real-world observational studies would help researchers better understand transmission patterns for COVID-19 in different community settings.
If you are studying a cancer drug it’s more defined and thus easier to perform a RCT, she said. With COVID it’s a “little messier,” she said, noting that it is harder to account for variables such as the type of places people are going and their compliance with masking.
Dr. Prasad, the Californian epidemiologist, doesn’t buy that criticism.
“When there are multiple randomized controlled trials, that’s what we take,” he said. “And the randomized trials are deadly sobering.”
He said the reason it isn’t a good idea to use observational studies to determine mask efficacy is that when you compare places that mask with places that don’t there are too many intervening variables, from differing attitudes on vaccines, to a community’s willingness to take COVID precautions, to politics and even the propensity of residents to report having COVID-19.
“Randomization doesn’t balance all the confounders,” Prasad said, “but what it does is equilibrate the outcome distribution in the absence of therapeutic effect, so you can isolate the treatment effect.”
Even as the case for broad mask mandates has taken a hit, public health experts at the national and state level in Michigan continue to stand by Covid-19 masking guidelines, at least in certain circumstances.
But Bagdasarian acknowledged that state guidance now is focused on looking at individual risk factors and the type of risks individuals may be facing. It’s still a very reasonable recommendation to mask, especially for people who are immunocompromised or at high risk, she said.
The truth, said Dr. Prasad, is that the U.S. needs to perform more randomized controlled trials on the effectiveness of masking.
Cochrane authors hinted at a similar conclusion, writing the “low to moderate certainty of evidence means our confidence in the effect estimate is limited.”