Two surgical masks.
Illustration: PGN

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What you need to know

  • The effectiveness of masks depends on their quality and fit.
  • We need better data to determine whether masks help slow the spread of viruses at the community level.
  • No prevention method is 100 percent effective—that’s why layering up on protection is your best bet at avoiding infection.

Three years into the pandemic, we’re still debating the effectiveness of masks against COVID-19. After a new review of mask studies concluded that it’s uncertain whether face coverings slow the spread of viruses like COVID-19 and the flu, many people interpreted the findings to mean that masks don’t work. But several scientists have pointed out that it’s much more complicated than that. Here’s what we know (and don’t know) about masking.

Can masks protect me against COVID-19?

High-quality masks, if worn correctly, can protect you against COVID-19. The virus spreads through particles, such as droplets and aerosols, which masks help filter. Studies have shown that masks can significantly reduce the number of COVID-19 virus particles you inhale, which in turn can lower the chance that you get infected. But the effectiveness of your mask depends on its quality and fit. N95 masks work best against both droplets and aerosols, while surgical and cloth masks don’t work as well against aerosols. Masks also become less effective when they don’t fit snugly on your face, as gaps give particles a chance to sneak through and enter your airways.

Can masks slow the spread of COVID-19 in my community?

It’s less clear whether masks are effective at slowing the spread of COVID-19 at the community level. This is a difficult question to investigate because, even when mandated, not everyone wears masks and those who do may not wear them properly. So far, studies have found a range of effectiveness of masking against COVID-19. Recently, some scientists tried to find an “overall” answer by looking at evidence from more than a dozen existing mask studies. They concluded that they’re “uncertain” about whether masks slow the spread of respiratory viruses like COVID-19 and the flu. They also acknowledged that the “relatively low numbers of people” who followed mask guidance may have affected the quality of their evidence.

How can I use a mask more effectively?

First of all, it’s important to wear high-quality, well-fitting masks. N95 and KN95 masks are the best at filtering out particles like droplets and aerosols, both of which contribute to the spread of COVID-19. A mask that fits snugly on your face will also help prevent COVID-19 virus particles from reaching your airways. Second, it’s important to view masks as just one layer of protection. No prevention method—whether it be vaccines, boosters, masks, or hygiene—is 100 percent effective. That’s why layering up on protection is your best bet at avoiding COVID-19 infection.