Is it time to start double-masking? That’s the question many people may be asking themselves as they seek additional protection from a pandemic that refuses to let up.

New research has shown that masks with multiple layers do a better job of blocking the COVID-19 virus from entering the mouth or nose. Indeed, it’s the number and kinds of layers, rather than the number of masks, that can make a difference in protecting you from infection.

That’s the reason why Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases and presidential advisor, has said that wearing two masks – providing a few extra layers – “likely would be more effective” than one mask alone.

It’s important to know that double-masking isn’t necessary for everyone, or every situation. Experts are recommending double-masking for riskier settings, such as when you’re indoors with people outside of your family or in enclosed spaces, like a train or airplane. Even so, it’s a good idea now to think about upgrading your mask so it fits properly and has at least two high-quality, breathable layers.

Here’s what you need to know about double-masking:

How to choose the highest level of protection. N95 masks offer the best protection, but these are still in short supply and should be reserved for health care workers. Otherwise, you have two options to achieve the maximum level of protection.

• Wear a cloth mask tightly on top of a surgical mask, where both work together to provide extra filtration and improve the fit.
• Wear a three-layer mask with outer layers made of a flexible, tightly woven fabric and a middle layer that contains a high-efficiency filter (e.g., vacuum bag material).

In either case – or if you decide that a single, multilayer mask is right for you – make sure your masks fit snugly without gaps around the edges. Masks that are made of flexible materials, feature nose bridges and have ties instead of ear loops can help create that tight fit.

Avoid going overboard by wearing more than two masks. Additional masks offer hardly any extra protecton, and they could make it much more difficult to breathe.

More layers create a tougher “obstacle course.” Masks work by blocking or filtering out the virus as air passes through them. The virus can be “caught” by a cloth mask’s fibers or “stuck” to the material of a surgical mask. Bouncing up against additional layers, the viral particles have a more difficult time navigating through this “obstacle course.”

A single, two-layer mask can filter out about 50 to 70 percent of small respiratory droplets. On the other hand, two masks or a three-layer mask can protect against more than 90 percent of these tiny particles.

Why extra precaution is needed. There are three main reasons why upgrading your mask makes sense. One, the number of cases remains very high, so there is a lot of virus circulating in the community. Two, new variants of the virus appear to be more contagious, meaning someone could become ill with less exposure to an infected person. And three, people are spending more time indoors during the winter, where the virus can linger and make infection more likely.

For now, vaccines won’t end the need for masking. While the authorized vaccines effectively protect an individual against infection, it still hasn’t been proven how exactly these vaccines will stop the spread of COVID-19 from one person to another. And besides, there are more people in our communities who aren’t vaccinated compared to those who are. For these reasons, proven measures like mask-wearing and physical distancing remain crucial aspects of our public health response.

Masks work, period. However you decide on which mask to choose, know that a growing body of evidence shows masks' effectiveness in preventing COVID-19 transmission. In one study that tracked Kansas during a surge last summer, COVID-19 cases decreased in 24 counties with mask mandates but continued to increase in 81 counties without them. In another, universal mask wearing required at a group of Boston hospitals led to a significant drop in positive COVD-19 tests among their staff.