“Laboratory studies indicate that masks, especially N95 respirators, can help reduce virus transmission. But as Flam notes, “the benefits of universal masking have been difficult to quantify” in the real world, where cloth models predominate and masks may not be clean, well-fitted, or worn properly.
The strongest real-world evidence in favor of general masking comes from a randomized trial in Bangladesh, which found that the use of surgical masks reduced symptomatic infections by 11 percent. That’s not nothing, but it’s a pretty modest effect, and it was achieved with surgical masks worn by adults in conditions that encouraged proper and consistent use. The same study found that cloth masks did not have a statistically significant effect.”
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“Given the situation during the omicron surge, there are additional reasons to doubt that mask mandates, even with perfect compliance, had much of an impact. While mandates required shoppers to don masks before entering supermarkets, for example, the risk of transmission in such settings is low, given the amount of time customers usually spend in them, the size of the air space, and typically wide distances between patrons. Conditions in bars and restaurants are more conducive to virus transmission, since customers spend more time there in closer proximity to each other, often while talking. But since people were allowed to remove their masks while eating and drinking, requiring them to cover their faces upon entry was more a symbolic gesture than a serious safeguard.
Beyond the question of how effective masking is in practice, there is the question of what impact mask mandates have on behavior. Even if masking works, that does not necessarily mean mandates do.
An Annals of Epidemiology study published last May found that mask mandates in the United States were associated with lower transmission rates from June through September 2020. “The probability of becoming a rapid riser county was 43% lower among counties that had statewide mask mandates at reopening,” the researchers reported. But the study did not take into account other policies or voluntary safeguards that may have differed between jurisdictions with and without mask mandates. Nor did it look at actual mask wearing, as opposed to legal requirements.
Based on data from various countries and U.S. states from May to September 2020, a preprint study published last June found that general mask wearing was associated with a reduction in virus transmission. But the researchers found no clear relationship between mask mandates and mask use. “We do not find evidence that mandating mask-wearing reduces transmission,” the authors reported. “Our results suggest that mask-wearing is strongly affected by factors other than mandates.”
An August 2021 systematic review of 21 observational studies found that all of them “reported SARS-CoV-2 benefits” from mask mandates “in terms of reductions in either the incidence, hospitalization, or mortality, or a combination of these outcomes.” But “few studies assessed compliance to mask wearing policies or controlled for the possible influence of other preventive measures such as hand hygiene and physical distancing.”
Like the debate about lockdowns, the debate about mask mandates will continue. Because there are so many variables to account for, it is very difficult to isolate the impact of any given policy. But it seems clear that anyone who takes it for granted that mask mandates have played a crucial role in controlling the spread of COVID-19 is making a series of assumptions that are not justified by the evidence.”