Do Face Masks Work?

Yahoo

10-03-2025

This week marks five years since March 13, 2020, the day President Donald Trump declared a national state of emergency over the novel coronavirus outbreak. The White House issued the President's Coronavirus Guidelines for America three days later. Among other things, the guidelines advised Americans to avoid bars, restaurants, shopping trips, and social visits. They also said that governors in states with evidence of community transmission should close schools, bars, restaurants, food courts, gyms, and other indoor and outdoor venues.
Sticking to peer-reviewed science, and setting aside the political question of what the government should do with the information, what do we know now about the ways people tried to protect themselves from the virus? Over the next few days we'll look at several measures—ivermectin, hydroxychloroquine, the vaccines—as well as the matter of how many Americans died of COVID infections. Today we'll tackle face coverings.
Early in the pandemic, National Institute of Allergy and Infectious Diseases chief Anthony Fauci notoriously announced on 60 Minutes that Americans "should not be walking around with masks." This was a reprise of Surgeon General Jerome Adams' February 29 tweet: "Seriously people. STOP BUYING MASKS!" Adams added, "They are NOT effective in preventing general public from catching #Coronavirus, but if healthcare providers can't get them to care for sick patients, it puts them and our communities at risk!"
A little over a month later, the government did an abrupt U-turn, with Trump announcing on April 3 that the surgeon general and the Centers for Disease Control and Prevention were now recommending that Americans voluntarily wear cloth masks in public to slow the spread of the coronavirus. Federal officials still wanted to reserve surgical masks and N95 masks for frontline health care workers.
States then began introducing requirements that individuals wear face coverings in public. By the end of the year, 39 states would adopt such measures.
These contradictory signals helped politicize facial masks. The controversy was further stoked by a January 2023 Cochrane Library analysis that was widely interpreted by many, including some of my Reason colleagues, as concluding that "masks don't work." In March 2023, Cochrane's editor issued a statement. "Many commentators have claimed that a recently-updated Cochrane Review shows that 'masks don't work', which is an inaccurate and misleading interpretation," wrote Karla Soares-Weiser. "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."
It takes at least two sides to politicize an issue. A July 1, 2020, op-ed in The New York Times compared refusing to wear a mask to "driving drunk" and the San Francisco Examiner on July 15, 2020, asserted "not wearing a mask makes you selfish, not an independent thinker." Mask skeptics were denounced as "covidiots."
Five years after the COVID-19 emergency was declared, has more conclusive evidence emerged one way or the other?
Masks are a big category: There are cloth masks, surgical masks, N95 respirators that block 95 percent of small particles. People use them both as source control—that is, to reduce the spread of respiratory droplet to others when an infected person talks, sneezes or coughs—and as respiratory protection for uninfected wearers.
A June 2024 meta-analysis in the journal Clinical Microbiology Reviews synthesized evidence from more than 100 studies and reviews. It found that masks, "if correctly and consistently worn," are "effective in reducing transmission of respiratory diseases and show a dose-response effect." It also found that, N95 and KN95 masks were more effective than surgical or cloth masks. Using data from jurisdictions with mask mandates, the researchers concluded that "mask mandates are, overall, effective in reducing community transmission of respiratory pathogens." The efficacy of masks alone does not settle the question of mask mandates, which is far more complex.
In their comprehensive 2024 report, Effectiveness of masks and respirators against respiratory infections, researchers associated with the Finnish Institute of Occupational Health reviewed 153 research articles on the effectiveness of mask use against infective agents or airborne droplets and particles. They reported that 128 of the articles they analyzed found masks to be effective. They noted that "systematic reviews of on randomized controlled trial studies in clinical or community settings demonstrated effectiveness in 10 out of 16 studies, and 20 out of 23 studies found mask mandates to be effective."
A July BMJ 2024 article reported the results of a randomized controlled trial by a team of Norwegian researchers. They assigned half of their cohort of nearly 5,000 subjects to wear three-ply surgical masks in public spaces—shopping centers, streets, public transport, etc.—over a 14-day period. The researchers reported that 163 participants of 2,371 assigned to wear face masks versus 239 of 2,276 of non-wearers self-reported respiratory symptoms. The researchers concluded that "the results support the claim that face masks may be an effective measure to reduce the incidence of self-reported respiratory symptoms consistent with respiratory tract infections, but the effect size was moderate."
In February 2025, the BMJ published a review evaluating the role of masks and respirators in preventing respiratory infections in health care and community settings. The British team noted the difficulty of evaluating studies conducted in the midst of an ongoing epidemic, but it concluded that "there is ample evidence on the effectiveness of masks and respirators in community and healthcare settings to inform consistent policy." It also concluded found that community mask use is effective during periods of increased transmission.
The Finnish report noted that several early randomized controlled trials did not find community masking to be effective at preventing respiratory illnesses. In a March 2024 article in the Journal of the Royal Society Interface, two researchers at Columbia University probed the discrepancy between mask efficacy as measured by laboratory experiments versus randomized controlled trials out in the real world. They found that individual masking behaviors—most specifically, disease transmission within households where masks are rarely used—limits mask efficacy in randomized controlled trials. Nevertheless, the researchers concluded that at the individual and population levels, masking effectively reduces the risk of infection and lowers epidemic intensity.
Upshot: From the perspective of five years, most research finds that facial masking is at least modestly effective for preventing and slowing down the spread of respiratory illnesses like COVID-19.
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