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Can universal masking prevent the need for future lockdowns? CDC says wear masks to protect yourself and others

Increasing universal masking by 15% could also reduce associated losses of up to $1 trillion in the US, says economic analysis

In its strongest messaging yet on face coverings, the US Centers for Disease Control and Prevention (CDC) has said that “adopting universal masking policies” can help avert future lockdowns, “especially if combined with other non-pharmaceutical interventions” such as social distancing, hand hygiene, and adequate ventilation. The new guidelines also say that wearing masks provide a two-way benefit: it not only protects others from the spread of Covid-19, but it protects the wearer as well.

According to the agency, coronavirus is mainly transmitted by respiratory droplets generated when people cough, sneeze, sing, talk or breathe. The CDC currently recommends community use of masks, specifically non-valved multi-layer cloth masks, to prevent transmission of Covid-19. 

The updated advisory continues to emphasize that masks are primarily intended to reduce the emission of virus-laden droplets -- source control -- which is especially relevant for asymptomatic or presymptomatic infected wearers who feel well and may be unaware of their infectiousness to others, and who are estimated to account for more than 50% of transmissions. However, it now stresses that masks also help reduce inhalation of these droplets by the wearer -- filtration for personal protection. Accordingly, the community benefit of masking for coronavirus control is due to the combination of these effects, and individual prevention benefit increases with increasing numbers of people using masks consistently and correctly, suggest guidelines. “Experimental and epidemiological data support community masking to reduce the spread of SARS-CoV-2. The prevention benefit of masking is derived from the combination of source control and personal protection for the mask wearer. The relationship between source control and personal protection is likely complementary and possibly synergistic so that individual benefit increases with increasing community mask use,” explains the scientific brief. It adds, “Further research is needed to expand the evidence base for the protective effect of cloth masks and in particular to identify the combinations of materials that maximize both their blocking and filtering effectiveness, as well as fit, comfort, durability, and consumer appeal.”

The statements are a departure from CDC’s previous softer approach suggesting the main benefit of wearing a mask was to help prevent infected people from spreading the virus to others, and that “the latest science may convince” people to wear masks. “This messaging is key to increase adherence and interest in mask-wearing. I am thrilled!” Dr Monica Gandhi, a professor of medicine with the University of California, San Francisco, tweeted. 

The new report comes amid a growing push to require mask use. President-elect Joe Biden has implored all Americans to cover their faces as a way to slow the spread of Covid-19. The Biden-Harris administration has also released a plan to beat Covid-19 which calls for a nationwide mask mandate. 

The guidance lists seven studies, which it says have confirmed the benefit of universal masking in community-level analyses. “Each analysis demonstrated that, following directives from organizational and political leadership for universal masking, new infections fell significantly. Two of these studies and additional analysis of data from 200 countries that included the US also demonstrated reductions in mortality,” reveals the brief.

The document also highlights an economic analysis using US data, which found that “increasing universal masking by 15%” could prevent the need for lockdowns and reduce associated losses of up to $1 trillion or about 5% of gross domestic product. Dr Saskia Popescu, an infectious disease epidemiologist and infection preventionist, tweeted: “We know that even fabric masks offer some variable protection for the wearer, but I think the bigger issue is that the CDC has to reiterate this to get people to wear a mask. Meaning that we’ve had to move beyond source control, but now personal gain to get ppl (people) to mask up.” Dr Angela Rasmussen, a virologist from Columbia University, agreed. “At the end of the day, I hope this encourages people to wear masks. I just wish we didn't have to encourage people to care for their communities by appealing to individual interests.”

What’s the explanation?

Stating that multi-layer cloth masks block the release of exhaled respiratory particles into the environment, along with the microorganisms these particles carry, the experts suggest that cloth masks not only effectively block most large droplets (20-30 microns and larger), they can also block the exhalation of fine droplets and particles. Often referred to as aerosols, these fine particles are smaller than 10 microns, which increase in number with the volume of speech and specific types of phonation. 

“Multi-layer cloth masks can both block up to 50-70% of these fine droplets and particles and limit the forward spread of those that are not captured. Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets, with cloth masks in some studies performing on par with surgical masks as barriers for source control,” notes the advisory.

On the subject of personal protection, the document cites studies that have demonstrated that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns. “Multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloth with lower thread counts, in some cases filtering nearly 50% of fine particles less than 1 micron,” it adds.

What do studies say?

The new document lists several studies regarding the “real-world” effectiveness of community masking. For instance, it cites the example of an investigation of a high-exposure event, in which two symptomatically ill hair stylists interacted for an average of 15 minutes with each of 139 clients for 8 days. The researchers found that none of the 67 clients who subsequently consented to an interview and testing developed an infection. The stylists and all clients universally wore masks in the salon as required by local ordinance and company policy at the time.

Another report of an outbreak aboard the USS Theodore Roosevelt, an “environment notable for congregate living quarters and close working environments,” found that the use of face coverings on-board was associated with a 70% reduced risk. 

Investigations involving infected passengers aboard flights longer than 10 hours strongly suggest that masking prevented in-flight transmissions, as “demonstrated by the absence of infection” developing in other passengers and crew in the 14 days following exposure, says the CDC.