The following was written by Public Health Insider, the blog for Public Health — Seattle & King County:

To help us get through the next phase of the pandemic safely, as the vaccine roll-out continues, a mask that’s well-made and fits well can make a big difference. Masks are one of the most important ways we can prevent COVID-19 – even with new, more contagious variants of the virus spreading.

There’s more evidence that wearing a mask protects everyone – the person wearing the mask (personal protection) and others around them (source control). Although masks alone are not 100% effective, they are a powerful tool.

“When everyone wears a mask, we’re all safer,” said Dr. Jeff Duchin, Health Officer for Public Health – Seattle & King County. “Always wear your mask whenever around people who don’t live with you, especially indoors.”

WHY ARE MASKS STILL SO IMPORTANT?

For starters, it’s important to remember that COVID-19 often spreads from people that look and feel well and who don’t have symptoms. So, we need to always take precautions. Also remember, the virus spreads primarily through the air, particularly with close contact. And (less commonly), it can also spread over longer distances indoors, especially when ventilation is not good.

That’s why we need to keep using multiple types of prevention at the same time – such as wearing masks, along with decreasing indoor activities with people who don’t live in your home, keeping as much physical distance from others as possible, avoiding crowded indoor spaces, improving indoor ventilation, and washing hands.

WHAT ARE THE MOST IMPORTANT CONSIDERATIONS WHEN SELECTING A CLOTH MASK?

Fit and filtration are the keys. Your mask should be:

• 2-3 fabric layers

• Made of tightly woven fabrics such as cotton and cotton blends

• Breathable

• Snug fitting, without gaps around the face

Wearing a mask with at least two layers is important. And for the mask to work well, a snug fit is key. Masks that are loose with gaps around your face or nose are not as helpful in protecting you or others.

HOW DO I KNOW IF MY MASK FITS PROPERLY?

The mask should snuggly cover your chin and nose, with no gaps. In order to more effectively filter out virus particles, your breath should go through the mask and not around the sides or out the top. If your glasses are fogging, the fit needs improvement. A nose wire in the mask helps improve the fit.

There are products, such as Fix the Mask and Badger Seal that you can add to your mask to improve the fit and prevent air leaking out the sides. This news report offers more details for how to improve mask fit.

WHY ARE 2+ LAYERS IMPORTANT?

The more layers you have, the harder it is for virus particles to get through. So, masks that have two or more layers are more effective at protecting the person wearing the mask and others around them.

There are a number of 2+ layer mask options. Cloth masks should have two or more layers. A filter acts as a layer, and some cloth masks have an option for a paper filter inside the mask, which adds a second or third layer.

Studies have shown that multiple layers of cloth with higher thread counts (tighter weave) have demonstrated superior performance compared to single layers of cloth with lower thread counts. Some other materials, such as polypropylene and silk, also can enhance the quality of a mask.

SHOULD I BE DOUBLE MASKING NOW?

Double masking (wearing two masks) is a way to add layers and create a snug fit. This improves filtration. That can be done by using two masks with a tighter fitting mask on top, or by making sure a single mask has multiple layers and fits very well.

IS A SURGICAL MASK OR N95 A BETTER OPTION THAN A CLOTH MASK?

Currently, the U.S. Centers for Disease Control and Prevention (CDC) doesn’t recommend “medical grade” FDA-regulated N95 masks or surgical masks for the general public. The main reason is to preserve limited supplies for healthcare workers and certain essential workers.

Although very effective when worn properly, N95 masks are expensive and remain in short supply. If enough affordable supplies and quality control standards were available, N95 or similar masks could be a potential option for use by the public, particularly in high-risk settings.

Some types of non-medical, disposable surgical-style masks are an option, but it can be difficult to determine the quality of these masks. In the absence of national standards for rating masks for the public, people can look for disposable surgical-style masks that are “ASTM” rated. If a surgical-style mask is worn, a snug fit is important just like with cloth masks

WHAT ABOUT KN95 MASKS?

Right now, we don’t have enough evidence to be able to make a recommendation for the public about using KN95 or similar masks. They might be as good or better than cloth masks, assuming they have a snug fit. But we don’t know enough yet about how to ensure the quality of these masks, as there is wide variation by manufacturer and the quality is not well-regulated.

If you order masks online, please beware that counterfeits and poor-quality masks are also sold.

IF I GET VACCINATED, CAN I STOP WEARING A MASK?

The vaccines are effective in preventing you from getting sick with COVID-19 (typically starting a couple of weeks after getting your second shot). But we don’t yet know if you may still be able to get infected with the virus and pass it on to others. At this time, everyone, including people who get vaccinated should continue to follow current public health guidance. This includes limiting close contact with other people outside your household, avoiding crowds, avoiding poorly ventilated indoor spaces, keeping as much distance as possible from others, washing hands frequently – plus consistently and correctly wearing a well-fitting, good quality face mask.

Ultimately, the most important tools against COVID-19 will be vaccines, but it will take many months before enough vaccines are available and enough people vaccinated to reach broad protection in our community.

Over time, as more people in the community are vaccinated, we will likely be able to relax other COVID-19 prevention measures that are currently needed. But definitely not yet.

Our understanding of masks continues to evolve, and Public Health will continue to update guidance as knowledge improves. We hope to see more information from the federal government on certification of effective masks for those who choose to upgrade.