Several states and numerous big-box stores have embraced new guidelines from the Centers for Disease Control and Prevention that say fully vaccinated Americans no longer need to wear masks indoors or out in most situations.

Friday afternoon, Walmart executives sent out a letter to Walmart and Sam's Club stores as well as supply chain facilities encouraging employees to get vaccinated. The letter noted that as of Friday, "vaccinated customers and members are welcome to shop without a mask," while unvaccinated shoppers are asked to keep wearing masks in stores.

Employees who are fully vaccinated will be permitted to work without masks starting May 18, the letter said, adding that some workers may have to continue to wear masks for health or sanitation reasons.

The letter added that "masks will also continue to be required by some city and state ordinances, and we will follow those requirements."

At Costco, vaccinated customers can shop without masks in US locations where there are no state or local mask mandates.

"We will allow members and guests who are fully vaccinated to enter Costco without a face mask or face shield," in those areas, the company said in a message posted to its website Friday. "Costco continues to recommend that all members and guests, especially those who are at higher risk, wear a mask or shield."

Costco won't require proof that customers have been vaccinated. Instead, the message said, "we ask for members' responsible and respectful cooperation with this revised policy."

All customers will still have to wear face coverings in Costco's pharmacy and other healthcare settings, the company specified. They will also have to wear them if they are in stores in locations where there are mask mandates.

In a news release issued Friday, Trader Joe's updated its mask policy and said fully vaccinated customers won't have to wear a mask while shopping.

Walt Disney World also announced changes to its mask rules for guests.

The resort located in Orlando, Florida announced Friday that masks and face coverings for guests will be "optional in outdoor common areas" at Disney World starting on Saturday. The exception being that guests "must wear face coverings from the entrances at all attractions, theaters or transportation and throughout those experiences," the company said.

So that means if you're walking down Main Street, U.S.A., you don't have to wear a mask but if you're riding Space Mountain, you'll still have to.

Universal Orlando Resort, a Disney competitor in Orlando that houses attractions from Harry Potter and Jurassic Park, also announced Friday that it was updating its COVID-19 safety measures. Like Disney's new requirements, it says that masks are not "mandatory" while outdoors but are still "required in all indoor locations including shops and restaurants" and required at all attractions.

Disney did not say if and when it would change mask guidance and safety measures at its other parks.

Disney's announcement airline stocks soaring, though the CDC guidance still calls for masks in crowded indoor settings such as planes, buses, trains, hospitals, prisons and homeless shelters, and says people should obey local and state regulations.

Other states and businesses took a wait-and-see attitude Friday amid questions of whether the new stand is safe or workable, given that there is no easy way to know who has been vaccinated and who hasn't. The guidelines essentially leave it up to people to do the right thing.

Labor groups and others warned that employees at stores, restaurants and other businesses could be left exposed to the coronavirus from customers and could be forced into the unwanted role of "vaccination police."

Several major chains, including Home Depot and grocer Kroger Co., announced that they would keep mask mandates in place for now.

But Sean Weinberg took down mask signs Friday at Restaurant Alba in Malvern, Pennsylvania, which he runs with his wife. He also emailed his employees to let them know they can forgo masks at work if they are fully vaccinated.

"It's just a headache we don't want to have to fight any more," he said of the mask requirement.

States such as Michigan, Nevada, Oregon, Pennsylvania, Minnesota, Kentucky, Washington and Kansas announced plans to fall in line with the CDC guidance either immediately or in the coming weeks.

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In a video statement, Oregon Gov. Kate Brown said the new approach makes clear that vaccines are the fastest way to get back to doing the things "we all love." Kentucky Gov. Andy Beshear called the guidance a "gamechanger."

"This is a heck of a benefit," Washington Gov. Jay Inslee said. "People who have been annoyed by this mask ... that shot is a ticket to freedom from masks." Read more at WBAL