White N95 masks with yellow straps sit on a table in the Clipper Room in Shriver Hall on the Homewood campus.

Credit: Will Kirk / Johns Hopkins University


You need a better mask. Why it's time to upgrade to an N95 or KN95.

More effective masks are needed to protect against the highly transmissible omicron variant of COVID-19, says Johns Hopkins expert Chris Beyrer, who also discusses proper mask care and when it's time to throw your mask away

The Centers for Disease Control recently changed its masking guidance for the public to include N95 and KN95 respirators, which offer better protection against COVID-19 infection compared to cloth or procedural masks.

With the highly transmissible omicron variant causing more than 18 million cases in the United States so far in January, it's time for a mask upgrade. Choices include an NIOSH-approved N95 mask, which the CDC says will provide the highest protection; a Chinese-certified KN95; or a Korean-certified KF94.

"The best masks are some version of N95," Eric Toner, a senior associate with the Johns Hopkins Center for Health Security, said in an interview with Reuters. "N95s, KN95s, and KF94s are functionally equivalent."

What's different about the use and care of these respirators compared with the surgical and cloth masks we've been wearing for the past two years? To find out, the Hub talked to Chris Beyrer, Desmond M. Tutu Professor of Public Health and Human Rights at the Johns Hopkins Bloomberg School of Public Health.

Why is it important to upgrade our masks?

Mask upgrades are largely driven by the extraordinary infectiousness of the omicron variant—it's at least twice as infectious as the delta variant, and delta was significantly more infectious than the earlier variants. In the vaccine arena, breakthrough infections are very common among immunized people who are not boosted. Boosting now is more important than it's ever been, but masking remains a key weapon in our arsenal to prevent infection. The other reality is we still have a big pool of kids under 5 who are not eligible for vaccination and who are going to daycare, preschool, and kindergarten who are vulnerable. So it's important for the adults around them to wear masks to maximize their protection. President Biden has opened up the strategic stock of masks, and that's good—that's where many of the N95s are coming from. The administration now feels that the manufacturing capacity is sufficient to keep this stockpile at the level it needs to be while also distributing masks to the public.

How do I know if I have a genuine N95?

It's tricky. First of all, the stores you buy from really matter. If you are buying online, it's important to first go to the CDC website, which has a very handy listing of what fake N95s look like and who are the reliable manufacturers and sellers. The other thing the CDC recommends is going to large purveyors—Walgreens, CVS, the kinds of places that connect to reliable distributors. If you don't see the NIOSH logo on an N95, it's not real.

Surgical or procedural masks and cloth masks alone are not highly recommended. But I think it's important to remember something that CDC Director Rochelle Walensky said just days ago, which is the best mask is the one that you actually will wear—I think this is especially true for young children.

Can I wear them more than once?

This is a little bit of a judgment call. If you are working at home and not wearing a mask during the day, and then you're going out to the pharmacy or the supermarket to buy supplies and you're wearing the mask for half an hour, you can wear it again. The challenge comes for people who have to wear them to work, or for people who have a known exposure. If you are actually caring for somebody with COVID at home, or you're in a clinical setting, then it's very different—masks should then be treated as disposable medical waste [after a day or after they are visibly soiled] and not reused. So it really depends on how you're using it and for what. My colleagues who have small children tell me their kids' masks get messy and dirty very fast.

An image of four types of face masks used to help prevent COVID-19 infection: from left to right, an N95, a KN95, a KF94, and a combination of a cloth mask and procedural mask.

Image caption: Johns Hopkins University currently requires masks in all indoor settings on campus and in university workplaces. Acceptable face coverings are, pictured from left to right, N95 masks, KN95 masks, KF94 masks, or combination of a cloth mask with a procedural mask.

How do you know when it's time to throw away an N95 or KN95?

We're all going to have to use our best judgment. Even for the ones that you're using just to go to the market or run errands, when it appears dirty to you, it's done. If you are sneezing a lot, or are caring for someone who has COVID, it will need to be replaced daily. If kids are wearing them to school, they might need to be replaced frequently depending on wear and tear and how soiled they are. Do not try to get N95s or KN95s wet—do not try to wash or clean them.

How do I store a mask in between uses—paper bags?

Cloth masks worn by children or worn paired with a surgical mask should be washed when they are dirty, and in between washings, they should be stored in a Ziploc bag to reduce the chance of exposure. The other kinds of masks—procedural masks and N95s or KN95s—if you want to reuse masks that aren't dirty, they can be stored in a paper bag. That will allow them to air out—whatever particles are there will desiccate and dry out.

Is it important that we now stick with these upgraded masks forever, or just until the omicron surge subsides?

We are hoping things are going to look quite different after the omicron wave, but we'll just have to wait and see on that for now. In occupational settings, on public transportation, on planes, masking mandates will be with us for a good long while. We have to get back to those low levels of community transmission before the mandates start to change. I'm not a modeler—I'm an old fashioned shoe-leather epidemiologist. But if you look at what the modelers are saying, they're all predicting that the big waves of hospitalization from omicron are not done in this country. The death wave is not done. But the infection curves are already bending in a couple of states like New York, Connecticut, and New Jersey, which had early omicron spikes. It would be wonderful if we follow the pattern we've seen in South Africa and the UK, which is a very rapid, explosive takeoff with an equally rapid fall once a high proportion of the population has had omicron. Assuming we don't have another infectious variant emerge, stronger masking mandates will be necessary through March, and then by April, you're going to see things start to really change for the better.