Should you still wear a mask indoors? It depends.

People wearing face masks indoors
People wearing face masks indoors. Is it safe to go maskless indoors? (Image credit: eclipse_images via Getty Images)

In May, the U.S. Centers for Disease Control and Prevention (CDC) issued new, less-restrictive recommendations for mask wearing for those who have been fully vaccinated against COVID-19. According to the most recent guidelines, vaccinated people can now go without masks in most indoor and outdoor settings, and unvaccinated people can forgo masks outside, as long as they're not in crowded settings. 

Due to the more contagious delta variant of the coronavirus, which is now spreading across the U.S. and other places, the World Health Organization is now recommending that even vaccinated individuals wear masks and social distance around other people. 

So is it really safe for vaccinated people to toss out their masks? According to two experts, the answer is mostly yes — with some caveats. 

As for fully vaccinated people removing their masks indoors, "In most cases, I would agree with this recommendation," said Dr. Thomas Kingsley, an assistant professor at the Mayo Clinic in Minnesota and chief epidemiologist at the PathCheck Foundation, a nonprofit that works on COVID-19 technology and research. "Studies have shown that all the currently available COVID-19 vaccines in the United States reduce the risk of getting COVID-19 and are highly effective in preventing severe disease and death." 

Related: Quick guide: COVID-19 vaccines and how they work

In other words, Kingsley said, vaccinated people can still get COVID-19, but their risk of becoming infected is now much lower. And if they do become infected, their symptoms are likely to be mild.

Still, some people should proceed with more caution. Namely, those who are not vaccinated should wear masks indoors, Kingsley said. And even some vaccinated people, particularly the elderly and those who are immunocompromised, should also continue to wear masks while indoors, Kingsley said. 

"There is less data on the clinical effectiveness of COVID-19 vaccines in those who are immunocompromised or older than 65 years old," Kingsley told Live Science. For example, the vaccine clinical trials excluded immunocompromised people, including some people with autoimmune disorders or those taking immunosuppressive medications. In addition, a 2020 study in the journal JAMA Internal Medicine found that people ages 65 and older were often excluded from  U.S.-based vaccine clinical trials. They also have a risk of dying from COVID-19 that's at least one order of magnitude higher than that of younger patients. Kingsley said both the immunocompromised and those over age 65 should be more cautious than CDC recommends and go maskless indoors only once they are vaccinated and community transmission of the virus has stopped.

One way to minimize the risk of severe COVID-19 even for those higher-risk groups would be to unmask indoors only when there are no reported cases in 45 days in a specific county or state, Kingsley said. During an outbreak, people's symptoms usually resolve around 15 days after they become infected, which means 45 days corresponds to about three generations of transmission, Kingsley said. So, if a community is not seeing many cases within 45 days, it is unlikely that there is a newer, undetected outbreak. 

Dr. Rachel Chasan, an infectious-disease physician at Mount Sinai Hospital in New York City, agreed with Kingsley that immunocompromised people fall into a gray area. "As the data is emerging, there are concerns that immunocompromised people may not be as well protected from infection," Chasan told Live Science. "Given this, those with an immunocompromising condition or taking an immunosuppressive medication should speak with their health care providers." 

She advised immunocompromised individuals to continue to be cautious regardless of their vaccination status. One way they can do this is to wear masks indoors,  she said. (For everyone else, wearing a mask is required on public transportation, such as at airports, and CDC recommends that even the vaccinated wear masks at crowded events, such as concerts.)

Another possibility is that people may be able to take off their masks, only to have to don them again in the future. We still don't know how long the immune response after vaccination lasts. And while the mRNA vaccines used in the U.S. work well against the known variants, we don't know  whether future variants will be able  to evade current vaccines, Kingsley said. (Little is known about the Johnson & Johnson vaccine's protection against variants.) In other words, he said, "Guidelines around mask wearing should be viewed as dynamic, with the possibility of changing as our research and the COVID-19 pandemic evolve." 

Chasan agreed. "Throughout the COVID-19 pandemic, we have had to repeatedly adapt to new scientific information," she said. "I expect that will continue in the weeks and months to follow."

Originally published on Live Science.

Jonathan D. Gelber
Live Science Contributor

Jonathan D. Gelber, MD, MS is an orthopedic sports medicine surgeon. He received his medical degree from Mount Sinai School of Medicine and earned a masters degree in Biomedical Engineering from Columbia University. His work has appeared in The Guardian, Newsweek, and Salon. He is also the author of  "Tiger Woods's Back and Tommy John's Elbow: Injuries and Tragedies That Transform Careers, Sports, and Society," (Sports Publishing, 2019). You can follow him on Twitter @JonathanGelber.