Throughout the pandemic, travelers forgoing masks has been a contentious subject. Travelers have refused to wear masks on flights and in popular tourist destinations. In parts of the world where masking is required in public, indoors or outdoors, run-ins with unmasked tourists have enraged locals who feel vulnerable as a result.

But today, following updated guidance from the Centers for Disease Control and Prevention, federal health officials announced that fully vaccinated Americans can forgo masks while outside, except in crowded settings.

While the outdoors have proven to provide a layer of safety during the pandemic, experts say certain conditions can increase risk, such as crowding, duration and high community transmission. As a result, there are outdoor situations in which masking is still recommended, even for the inoculated.

Today’s news comes on the heels of another major milestone from the CDC, when this month it said fully vaccinated people can travel — although the agency doesn’t encourage it.

As more Americans get vaccinated before they fly, sail and drive, when should travelers mask outdoors? We spoke with health experts to find out.

When you’re traveling somewhere where it’s required

Even though U.S. health authorities have loosened outdoor mask restrictions, J. Tashof Bernton, a board-certified occupational medicine specialist and president of ImmunaBand, says travelers should be prepared to follow different masking rules depending on where they are visiting. While the United States is rapidly vaccinating its population, that’s not the case in other countries.

“US citizens may be under the impression that conditions in the United States mirror those around the world,” he said in an email. “They do not, and many countries are facing serious challenges from Covid that will dramatically affect travelers, regardless of their vaccination status.”

When choosing whether to mask outdoors, default to the local mandates.

When travelers are outdoors in crowded places

Kacey Ernst, a professor of epidemiology at the University of Arizona College of Public Health, acknowledges that breakthrough transmission risks outdoors are much lower than indoors, but “not all outdoor spaces are the same.”

“Some are very sparsely populated — think hiking trails in remote areas. Others are much more crowded — outdoor festivals, concerts, etc.,” she said in an email.

Special pathogens expert Syra Madad, who was featured in the Netflix docuseries “Pandemic: How to Prevent an Outbreak,” says if travelers know they’re going to be close to strangers in a crowded setting, “then you want to continue to wear a mask.”

Her advice changes if you know you will be in a crowd of fully vaccinated people, or depending on the layout of the crowd. Travelers can use their best judgment.

“If you’re in a crowd with [vaccinated and unvaccinated] people, but they’re distant enough, then you can look at not wearing a mask,” Madad says. “But if there’s a lot of people very close together … then you may want to look and see, ‘Is that a good idea for me not to wear a mask?’ ”

When you’re traveling somewhere with high coronavirus transmission

Andrew Peterson, assistant professor at the Institute for Philosophy and Public Policy at George Mason University and a guest researcher at the National Institutes of Health, says because places are experiencing varying coronavirus caseloads, it’s important to be responsible when traveling — particularly where highly infectious variants are circulating, such as Michigan and Puerto Rico.

Citing that concern, Madad says travelers should consider coronavirus case numbers of the place they’re visiting as they make masking decisions.

There are areas in America where transmission is low enough that if you’re outdoors, not in a crowded setting, “then certainly you don’t have to wear a mask,” she says.

However, she warns those traveling abroad to stay vigilant with coronavirus precautions, or rethink your international travel plans entirely, after the State Department’s recent move to give roughly 80 percent of countries the “Level 4: Do Not Travel” designation.

“It’s not a good idea to go to a lot of these countries that have very high levels of transmission because of the variants that are circulating,” she says.

When you’re traveling with non-vaccinated people

Madad says if you’re traveling in mixed company, masking may still make sense outdoors when you’re not able to stay apart.

“I would want to continue to wear my mask because it would be hard for me to keep my distance if we’re all going together,” she says.

Brandon Brown, an epidemiologist and a public health and medical ethics associate professor at University of California at Riverside, agrees that vaccinated people should definitely mask outdoors when traveling with non-vaccinated companions. He advises travelers to remain vigilant about masking when they’re around anyone outside of their household, even though outdoor transmission risk is low.

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