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A Project of The Annenberg Public Policy Center

Video: The Science Behind Shifting COVID-19 Face Mask Advice


In this video, we explore the existing research on face masks as tools to limit the spread of infectious diseases and explain why the Centers for Disease Control and Prevention changed its stance on whether people who aren’t sick need to cover their faces.

In the initial months following the outbreak of COVID-19 — the disease caused by the novel coronavirus — the CDC cautioned against widespread face mask use, recommending masks only for people who were ill or those who were treating them.

But on April 3, in light of new evidence that a “significant portion” of infected people spread the virus to others even when they don’t have symptoms, the agency began recommending that people use cloth face coverings anytime they leave their homes and can’t stay six feet away from other people. 

The shifting advice was welcomed by some experts, who say cloth face coverings are likely to be better than nothing. Masks are thought to primarily prevent people from spewing infectious droplets from their noses and mouths and infecting others.

But other experts have reservations, given a lack of clinical trials that demonstrate surgical masks are useful in the general population. And there are concerns that the new guidelines could exacerbate shortages of medical masks for the health care workers who need them most — or backfire if people don’t wear their coverings properly or are lulled into a false sense of security.

Despite the debate, experts agree that medical masks need to be prioritized for health care workers and that it’s still best for people to stay home. As the CDC says, cloth coverings are “not a substitute” for social distancing.

For more information about face masks and what the research and experts think about their use during the COVID-19 pandemic, see our story, “COVID-19 Face Mask Advice, Explained.”