Known factors, unanswered questions, and opportunities to increase adoption.
The evidence is overwhelming: Wearing a mask prevents coronavirus transmission. But unlike some countries, the United States hasn’t embraced mask-wearing.
Part of the problem is a lack of clear, consistent guidelines. And sociopolitical factors also make Americans resistant to safety guidelines, even when they are clearly communicated. But the masks themselves also present some problems. The most effective masks are still in short supply and should be reserved for frontline health workers; meanwhile, masks intended for the general public vary widely in comfort, efficacy, cost, and availability.
Absent a national mask-wearing mandate, we must quickly find ways to get more people wearing masks — any kind of available face covering. We know this simple act can blunt transmission and help communities resume everyday activities while we live with the coronavirus. At the same time, we need to work on developing better reusable masks that provide both comfort and protection.
This week, we’re looking at the known factors and unanswered questions related to mask-wearing, as well as opportunities to make better masks and get everyone to wear them.
What we know
Current policies and guidance.
- At the beginning of the pandemic, the CDC did not recommend members of the public wear masks. (At that time, experts had a limited understanding about asymptomatic transmission and the efficacy of masks, and there were also concerns about a lack of supply for frontline workers.) The CDC now recommends that all people over the age of two wear cloth face coverings in public settings and when they are around people they don’t live with, especially when social distancing is difficult to maintain.
- Many countries have recommended or mandated masks — some across the entire country, others in areas with high infection rates or in specific settings, such as supermarkets.
- Currently, most states require people to wear masks, at least in some locations, but this requirement varies across states. Mandatory mask laws also mean many different things; some require people to wear masks anytime they leave the house, others only require masks in specific settings, such as on public transport or in essential businesses.
- Compliance and enforcement also vary: In some states, authorities have announced fines for non-compliance, but police have said they won’t enforce these rules.
Effectiveness of masks.
- A growing body of evidence supports mask-wearing. Most studies point to the role of masks in preventing the wearer from transmitting COVID-19 to others, but masks can also protect the wearer and even reduce the severity of COVID-19.
- Studies have assessed masks’ effectiveness in different ways: Some conducted in laboratories demonstrate how different materials block respiratory droplets. Others have looked at real-world scenarios — such as the changes in case rates before and after the introduction of mask mandates. A NIST engineer set up an at-home lab to test different types of face coverings; even the simplest face coverings prevented a cough from landing on someone nearby.
Different types of masks.
- How much protection a mask provides — both to the wearer and to the people around them — depends on the type of mask and whether it is worn correctly.
- Cloth masks should be made with multiple layers of materials with a tight weave. Experts recommend avoiding masks with exhalation valves. Those who use cloth masks should wash them by hand with soap and water or add them to their normal laundry.
- N95 masks can block at least 95% of small airborne particles; this means they protect both the wearer and the people around the wearer. But experts say these are still in short supply and should be reserved for frontline healthcare workers.
- KN95 masks are similar to the N95, but there are concerns about merchants selling counterfeit masks. Check Appendix A of the Food and Drug Administration’s emergency use authorization to see if a particular model is authorized.
- Surgical masks can block the majority of respiratory droplets emitted from an infected person, but the extent to which these protect wearers can vary widely.
- For all types of masks, sanitary practices are important. The Mayo Clinic recommends people wash or sanitize their hands before and after putting on or taking off their masks, and people should avoid touching masks while wearing them.
What we don’t know
Comparing and combining masks with other prevention measures.
- Experts suggest masks should be worn in conjunction with other measures, such as social distancing and hand hygiene. And multiple studies indicate that wearing masks and other protective gear can also increase adherence to social distancing guidelines.
- We do not have real-world examples of scenarios in which masks alone have prevented outbreaks. One study that looked at airborne transmission before and after masks were introduced found masks to be the most effective prevention measure. Another study analyzed multiple variables contributing to coronavirus death rates in 198 countries and found the countries that introduced masks at the beginning of an outbreak had far fewer deaths than countries that waited. Researchers have also documented specific instances — including at a salon and on an airplane — in which a mask-wearing, COVID-positive person has not spread the virus to others.
- What level of compliance is needed? One model suggests that “when lockdown periods are combined with 100% face mask use, disease spread is vastly diminished, preventing resurgence for 18 months.” Another model predicts that 80% of the population wearing masks dramatically reduce the spread of COVID-19 — without a strict lockdown.
- When should people wear masks, and when is it safe to take them off? Current guidance is often unclear when it comes to wearing masks in specific everyday situations, such as exercising outdoors.
Making better masks available
Designing and distributing improved masks.
- High-filtration masks designed for use by the general population “would give people control over their own safety, a greater incentive to wear them, and the confidence to resume economically important activities.” These masks should meet five parameters: protection, scalability, comfort, reusability, and style.
- Unfortunately, existing mask choices carry a tradeoff; masks with better coverage and protection are less breathable and less comfortable. Respondents to an ongoing XPrize survey say that the heat, fogged-up glasses, breathing difficulty, and lack of comfort were their main concerns about wearing a mask. The Next-Gen Mask Challenge is asking young innovators to design face masks that are “more comfortable, functional, accessible, and even stylish.”
- Reusability is also a consideration: The enormous scale of the pandemic means that single-use masks and gloves can make a negative environmental impact. MIT has developed a reusable mask based on the N95 model; it is made out of silicone, so it could be easily sterilized and reused, reducing environmental impact and cost.
- Some governments are paying for masks: New York City is currently distributing free surgical masks in parks, grocery stores, and other locations, and the French government has distributed 40 million masks to low-income households.
Getting everyone to wear masks
Culture, politics, and identity.
- A survey of 2,500 people in the U.S. found that women were more likely to wear a face covering than men, but this difference subsided where masks weren’t mandatory. The same study found that messaging emphasising the risk to “your community” had a bigger impact on encouraging mask usage than messaging that emphasized the risk to “you,” “your family,” or “your country.”
- A Pew survey conducted in late June found Democrats are more likely than Republicans to say they wore a mask all or most of the time in the past month (76% vs. 53%). It also found that those over 65 are more likely to say they have worn a mask in the past month than 18 to 29-year-olds (74% vs. 62%).
- A clear federal mask mandate could go a long way toward closing gaps in adherence: An evidence review found that universal mask-wearing policies can lessen stigma and heighten solidarity.
Enforcement and adoption.
- During the 1918 flu pandemic, authorities presented mask-wearing as a civic duty — building on the patriotic messaging used during WWI — and some states introduced punitive measures such as short jail terms and fines from $5 to $200 for failure to comply.
- Experts suggest we look at examples of building habits around other routine safety measures, such as wearing seatbelts, helmets, and condoms. To follow suit, we should make masks freely available, normalize their use, and help people negotiate social situations.
- UCSF: Still confused about masks? Here’s the science behind how face masks prevent coronavirus.
- Wall Street Journal: How face masks work and which types offer the best COVID-19 protection.
- NPR: A user’s guide to masks: What’s best at protecting others (and yourself).
- Royal Society DELVE Initiative: Report on face masks for the general public.
- De Kai: Universal Masking white paper and visual simulation.
- NIST: My stay-at-home lab shows how face coverings can slow the spread of disease.
- Preprints: Face masks against COVID-19: an evidence review
- Harvard Business Review: We need better masks.