• The CDC said Thursday that fully vaccinated people no longer need to wear a face mask or stay 6 feet away from others in most settings, whether outdoors or indoors, drawing both praise and criticism.
• Disney said it planned to increase capacity limits at its U.S.-based theme parks, and The Wynn Las Vegas eased its own mask guidelines.
• Just six weeks ago, CDC Director Dr. Rochelle Walensky was warning people of "impending doom" as daily Covid-19 cases in the U.S. began to rise again.
• Business and health leaders said it is "nearly impossible" to police the use of face masks because there is no way to know who is vaccinated and who isn't.

Disney was quick to announce that it plans to further raise capacity limits at its U.S. theme parks a few hours after the Centers for Disease Control and Prevention announced relaxed mask guidelines for the U.S. on Thursday.

"[It's] big news for us, particularly if anybody's been in Florida in the middle of summer with a mask on," CEO Bob Chapek joked with analysts on an earnings call about two hours after the new recommendations were released.

"Given the guidance that just came today from the CDC, and earlier guidance that we got from the governor of Florida, we've already started to increase our capacities," he said.

The CDC now says fully vaccinated people no longer need to wear a face mask or stay 6 feet away from others in most settings, whether outdoors or indoors, according to the updated guidance. It's the first time the federal government has encouraged people to stop wearing masks since the agency first called for face coverings more than a year ago. It marks a major turning point in the Covid-19 pandemic in the U.S. and brings the country one step closer to normalcy. Public health experts also said the change is likely to encourage more Americans, especially those still hesitant about receiving the shots, to get vaccinated.

The agency, however, came under sharp criticism for its quick turnabout. Just six weeks ago, CDC Director Dr. Rochelle Walensky was warning of "impending doom" as daily Covid-19 cases in the U.S. began to rise again. And many health and business leaders say the new recommendations were too ambiguous. It requires essential workers to police vaccination records and will be difficult to enforce.

Vaccine police

"Under current plans, it will be impossible to enforce in most settings," Dr. Peter Chin-Hong, an infectious disease physician at the University of California San Francisco, told CNBC. "Businesses, schools and event organizers may still have purview in requiring evidence of vaccination prior to inclusion in specific communities or events, but for other everyday events there will be no enforcement in the way of vaccine passports or QR codes as done in other countries."

There are some instances where fully vaccinated people still need to wear masks: traveling by plane, bus or train as well as in certain places such as hospitals, nursing homes, prisons or at establishments that require them, the agency said. The CDC's guidance also isn't mandatory. States, municipalities and businesses can decide whether or not they want to follow it, increasing confusion for many business owners and employees.

Some health and law experts told CNBC it would further complicate public health efforts to end the pandemic, adding it is "nearly impossible" to police the use of face masks because there is no way to know who is vaccinated and who isn't. More than half of the population still haven't gotten the shots, they said, risking more outbreaks from unmasked, unvaccinated individuals.

"While we all share the desire to return to a mask-free normal, today's CDC guidance is confusing and fails to consider how it will impact essential workers who face frequent exposure to individuals who are not vaccinated and refuse to wear masks," Marc Perrone, president of the United Food and Commercial Workers Union, said in a statement. "Essential workers are still forced to play mask police for shoppers who are unvaccinated and refuse to follow local COVID safety measures. Are they now supposed to become the vaccination police?"

Creates ambiguity

Lisa LaBruno, senior executive vice president of retail operations and innovation for the Retail Industry Leaders Association, told CNBC the new guidance "creates ambiguity for retailers because it fails to fully align with state and local orders."

"These conflicting positions put retailers and their employees in incredibly difficult situations. We urge state and local governments to coordinate with the CDC as additional guidance is issued on the road to normalcy," she said in a statement.

Beauty store chain Ulta Beauty said it doesn't plan to change its mask and social distancing requirements in its stores, although it is actively assessing "the implications of this updated guidance for our guests and associates." It said the health and safety of its employees and customers was its top priority.

"I hate to say 'It's complicated,' but it's complicated," said David French, a lobbyist for the National Retail Federation. On one hand, the CDC guidance could bring more clarity, but it also makes things more complex since businesses won't know who is or is not vaccinated — and neither will customers.

Even with the milestone announcement, shoppers shouldn't expect to see immediate changes at their grocery store or local mall, said Joel Bines, global co-leader of the retail practice at consulting firm AlixPartners. He said the guidance will make little difference for retailers who do not know people's vaccination status — and above all, want to make sure their workers and customers don't get sick.

"This is an extremely difficult management problem for any business that interacts with consumers on a physical level," he said. "There is no operating manual for this."

Law professor Lawrence Gostin, director of the World Health Organization's Collaborating Center on National and Global Health Law, said the new guidance could have "serious unforeseen consequences."

"The public will not feel comfortable shopping, dining, or going to church or a gym if they have no idea whether the unmasked person standing next to them is vaccinated or not," Gostin said.

46% of U.S. population vaccinated

As of Thursday, more than 154 million Americans, 46.6% of the U.S. population, have received at least one dose of a Covid vaccine, according to the CDC. Roughly 118 million Americans are fully vaccinated, according to the agency. The U.S. government is working to persuade more Americans to get a vaccine after the pace of shots slowed in recent weeks.

Unlike some other countries, the U.S. doesn't have a system where people can prove they've been vaccinated. Even if there was one, vaccinated people are unlikely to always have their cards with them, and not everyone will have digital proof, said Dorit Reiss, a professor of law at UC Hastings College of Law. Areas with high vaccination rates can probably lift mask restrictions entirely, she added.

"This is an exciting and powerful moment," Walensky, the CDC director, told reporters at a White House Covid-19 briefing Thursday after announcing the new guidance. "It could only happen because of the work of so many who made sure we have the rapid administration of three safe and effective vaccines."

From an epidemiology standpoint, the CDC guidance "means we are at a place where we are at the best place in the pandemic we have ever been as a country with continued declines in infections, hospitalizations and deaths," said Chin-Hong.

"The symbolic meaning is even more palpable," he added. "Masks have been the symbol of fear and political divisiveness [and] by casting them off, at least for vaccinated folks, it hopefully means that this is returning us to the life that we aspired to pre-pandemic."

The Nevada Gaming Control Board, which sets the rules for casinos, immediately updated its rules, allowing The Wynn Las Vegas to ease its own mask guidelines. The company said Friday fully vaccinated guests and employees won't have to wear masks at its hotels and casinos.

Bowing to pressure

Gostin and others were critical of the CDC's abrupt change in policy, saying it's bowing to pressure from the public and governors to return to normal. "As a result, CDC is making momentous shifts in its guidance, lurching from over-caution to abandoning all caution," he said, adding that it could undermine public trust in the agency. "It will make the public rely less on CDC guidance if it feels the agency is being pushed around."

On Friday, Walensky defended the timing of the new guidance. Over the last two weeks, daily Covid cases have declined by over a third, she said, and vaccinations are now widely available in most places across the U.S. She added the guidance is "empowering" people to make decisions about their own health, urging unvaccinated people not to take the risk of going out unmasked.

If several people are in a room unmasked, the vaccinated people will be protected from getting Covid, she said.

Emerging science shows that vaccinated people are protected and have a "very low risk of transmitting" Covid to other people, even with some of the variants that appear to make the vaccines less effective, she said on "CBS This Morning." 

— CNBC's Nadine El-Bawab, Sarah Whitten and Michael Wayland contributed to this article.

Correction: This article was updated to reflect that Dr. Peter Chin-Hong is an infectious disease physician at the University of California San Francisco.