Is This COVID-19 Mask Efficacy Chart Accurate?

The CDC recommends wearing a cloth face mask in public during the COVID-19 pandemic to help slow the spread of the disease.

  • Published 21 April 2020

Claim

A chart accurately shows the effectiveness of wearing face masks during the COVID-19 pandemic.

Rating

Mostly False
Mostly False
About this rating

What's True

The CDC recommends wearing a cloth face mask in public to help slow the spread of coronavirus.

What's False

The percentages displayed in this chart cannot be accurate because no scientific consensus exists on the efficacy of homemade masks in stopping the spread of COVID-19.

What's Undetermined

The efficacy of face masks against the spread of COVID-19 is unknown.

Origin

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Wearing a face covering in public during the COVID-19 coronavirus disease pandemic is sound advice (and in some circumstances a legal requirement) that could help slow the spread of the disease, according to the Centers for Disease Control and Prevention (CDC). But just how effective are these masks? In April 2020, many social media users encountered a simple chart that supposedly showed how effective face masks could be at preventing coronavirus infections:

We’re skeptical about the accuracy of this chart. It doesn’t appear to have originated with a reputable source; this meme does not specify the type of mask (homemade cloth mask, surgical mask, or N95 mask) used in the chart; and we were unable to find any studies that confirm these specific percentages. 

We’ve seen this chart posted by a variety of accounts on several different platforms but have yet to come across any information about who created it. While we’re not certain if this chart was created by an anonymous social media user (social media has been a hotbed of bad medical information during the COVID-19 pandemic) or from a reputable organization, the evidence indicates that it came from the former. 

We were not, for instance, able to find this chart on the CDC website. The CDC even has a page dedicated to “Respiratory Protection Infographics,” but the above-displayed chart is not included on that page. This chart is also absent from the CDC’s page that recommends the use of cloth face masks during the COVID-19 pandemic.

The CDC confirmed to us that it did not create this chart and that the agency could not confirm the accuracy of these statistics. At the moment, a spokesperson told us, there is not enough data to “quantify risk reduction from the use of masks.”

The punctuation in this chart may provide a clue about its origins. While the percent sign is commonly placed after the number in English and many other languages, this symbol comes before the number in Turkish. As luck would have it, we found a variation of this chart in Turkish that has been circulating on Facebook since April 10:

In addition to this chart’s unknown origins, another reason to be skeptical of these numbers is that this social media post does not identify the type of mask being used. Is this chart about homemade cloth masks? Surgical masks? Or the N95 respirator mask? These masks all provide different levels of protection against the spread of disease, with the N95 being the most effective. 

The FDA explains the differences:

CDC Recommends Cloth Face Coverings for Use by the General Public: The CDC recommends that members of the public use simple cloth face coverings when in a public setting to slow the spread of the virus, since this will help people who may have the virus and do not know it from transmitting it to others.

Surgical Masks: … If worn properly, a surgical mask is meant to help block large-particle droplets, splashes, sprays, or splatter that may contain germs (viruses and bacteria), keeping it from reaching your mouth and nose. Surgical masks may also help reduce exposure of your saliva and respiratory secretions to others.

While a surgical mask may be effective in blocking splashes and large-particle droplets, a face mask, by design, does not filter or block very small particles in the air that may be transmitted by coughs, sneezes, or certain medical procedures. Surgical masks also do not provide complete protection from germs and other contaminants because of the loose fit between the surface of the face mask and your face.

N95 Respirators: An N95 respirator is a respiratory protective device designed to achieve a very close facial fit and very efficient filtration of airborne particles.

The ‘N95’ designation means that when subjected to careful testing, the respirator blocks at least 95 percent of very small (0.3 micron) test particles. If properly fitted, the filtration capabilities of N95 respirators exceed those of face masks. However, even a properly fitted N95 respirator does not completely eliminate the risk of illness or death.

The CDC elaborated on the purpose of wearing homemade cloth masks during the COVID-19 pandemic. The CDC writes that since many people with coronavirus may be “asymptomatic,” meaning that they don’t show any symptoms, wearing a cloth mask can prevent these contagious individuals from unknowingly spreading the disease:

CDC continues to study the spread and effects of the novel coronavirus across the United States. We now know from recent studies that a significant portion of individuals with coronavirus lack symptoms (“asymptomatic”) and that even those who eventually develop symptoms (“pre-symptomatic”) can transmit the virus to others before showing symptoms. This means that the virus can spread between people interacting in close proximity—for example, speaking, coughing, or sneezing—even if those people are not exhibiting symptoms. In light of this new evidence, CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission.

It is critical to emphasize that maintaining 6-feet social distancing remains important to slowing the spread of the virus. CDC is additionally advising the use of simple cloth face coverings to slow the spread of the virus and help people who may have the virus and do not know it from transmitting it to others. Cloth face coverings fashioned from household items or made at home from common materials at low cost can be used as an additional, voluntary public health measure.

The cloth face coverings recommended are not surgical masks or N-95 respirators. Those are critical supplies that must continue to be reserved for healthcare workers and other medical first responders, as recommended by current CDC guidance.

When we reached out to the CDC, a spokesperson reiterated this point, saying that wearing a mask is a good way of “strengthening the social distancing that we are already doing.”

A spokesperson for the CDC told us:

“As we study the virus, CDC has learned that a good proportion of individuals who have COVID-19 spread virus before they become symptomatic and a few people never have symptoms at all but are still infected and infectious. That means, that people who are not coughing or sneezing can be a source of infection for others. Something simple like speaking is enough to generate aerosols that can spread the infection to other people.

A simple cloth mask is a way to contain respiratory secretions right at the source and not put other people at risk. The mask traps the droplets before they spread into the environment. Therefore, “my mask protects you, and your mask protects me!” It’s a way of strengthening the social distancing that we are already doing.

The numbers provided in the above-displayed viral social media post are also suspiciously specific. While there have been studies regarding the efficacy of masks during COVID-19 pandemic, researchers are still learning about how this disease spreads and how to best prevent it. For instance, Live Science noted that two recent studies regarding the efficacy of face masks during this pandemic came to slightly different conclusions. 

Live Science writes:

For the first time, the Center for Disease Control and Prevention (CDC) has recommended that even seemingly healthy people wear masks over their mouths and noses when venturing out of their homes into places where it is difficult to maintain distance from other people. But there is still major debate over how much masks — particularly the homemade fabric masks that the CDC recommends for the public — can slow the spread of SARS-CoV-2, the virus that causes COVID-19.

Researchers, writing in two new papers, attempt to tackle the efficacy of masks, one more rigorously than the other, and come to differing conclusions. One study examined the effect of masks on seasonal coronaviruses (which cause many cases of the common cold) and found that surgical masks are helpful at reducing how much virus a sick person spreads. The other looked particularly at SARS-CoV-2 and found no effect of either surgical or fabric masks on reducing virus spread, but only had four participants and used a crude measure of viral spread.

The bottom line, experts say, is that masks might help keep people with COVID-19 from unknowingly passing along the virus. But the evidence for the efficacy of surgical or homemade masks is limited, and masks aren’t the most important protection against the coronavirus.

Some experts have also expressed concern that widespread use of homemade cloth masks give people a false sense of security. The White House’s coronavirus response coordinator, Dr. Deborah Birx, said that social distancing is still the most important preventative measure a person can take during this pandemic:

“The most important thing is the social distancing and washing your hands,” she said. “And we don’t want people to get an artificial sense of protection because they’re behind a mask. Because if they’re touching things — remember your eyes are not in the mask — so if you’re touching things and then touching your eyes you’re exposing yourself in the same way.”

The World Health Organization (WHO) reiterated this point. WHO said in a statement that “masks alone cannot stop the pandemic:” 

“Masks alone cannot stop the pandemic. Countries must continue to find, test, isolate and treat every case and trace every contact. Mask or no mask, there are proven things all of us can do to protect ourselves and others – keep your distance, clean your hands, cough or sneeze into your elbow, and avoid touching your face.”