More than a year after federal health officials told Americans to cover their faces when venturing out in public, the Centers for Disease Control and Prevention said today that fully vaccinated people could start taking off their masks indoors.

But the new federal guidance — announced amid a sharp decline in coronavirus cases and an expansion of vaccine eligibility to everyone 12 and older — came with caveats and confusion. And it sent state and local officials, as well as private companies, scrambling to decide whether and when to update their own rules.

Here are some questions you might have about what the CDC’s new stance means, and what it doesn’t mean.

Does this mean masks are no longer recommended anywhere?

Not quite. The federal guidance is expansive: Fully vaccinated people — those who have received their final COVID-19 vaccination at least two weeks ago — no longer need to wear masks outdoors or in most indoor settings. But there are limits.

The agency was not specific about masking in some settings, including schools. And even fully vaccinated people are still told to cover their faces when visiting health care facilities, while flying or taking public transit, and in congregate settings such as homeless shelters, as well as prisons or jails.

What does this mean for local mask mandates?

The CDC advice does not override mask orders issued by states, counties or cities. But in the hours after the new policy was announced today, officials in some parts of the country began to adjust their rules to align with federal guidance. Others had yet to weigh in publicly, and some said they were keeping their rules in place while they reviewed the CDC’s suggestions.

As the guidance filtered out around the country, officials began issuing announcements — a patchwork of plans, as so much of the nation’s pandemic response has been over the last year. Officials in Pennsylvania said they had changed the state’s mask mandate to exempt fully vaccinated people, and Gov. Andy Beshear of Kentucky and Gov. J.B. Pritzker of Illinois, both Democrats, indicated that they would do the same. The chief executive in St. Louis County, Missouri, said he was also working to update local restrictions.

Elsewhere, including in Wichita, Kansas, New York state, New York City and New Jersey, officials said they were reviewing the new guidelines but were not yet announcing any changes. In the counties that include Las Vegas and Lawrence, Kansas, officials said they would discuss their rules at meetings next week.

Was this a surprise?

The news stunned health experts, political leaders, business owners — and seemingly everyone else. Only 2-1/2 weeks ago, the CDC had given a far milder directive, saying that fully vaccinated people could remove their masks outdoors but not in crowded spaces.

“It feels like a huge shift, and I’m not going to follow it,” said Dr. John Swartzberg, an infectious-disease specialist and clinical professor emeritus at the University of California, Berkeley’s School of Public Health. “The most important point is that the CDC is putting responsibility back on individuals. Each individual should look at what the CDC is recommending and see if that fits for them.”

Swartzberg said he would continue to be unmasked while outdoors but would carry a mask with him to wear indoors in public spaces. “This shows tremendous confidence in how well the vaccines work,” he said. “The CDC does have data to support this decision. It’s not like they’re operating on the fly.”

Why now?

It was not entirely clear what prompted the new guidance today. Cases, hospitalizations and deaths have been trending downward in the United States for weeks. About 37,000 cases are being identified each day, the fewest since September, and about 630 deaths are being announced daily, the lowest average since July. But the most significant change is the availability of vaccines.

Everyone age 16 and older has been eligible for a vaccine for weeks, and those ages 12 to 15 became eligible for the Pfizer-BioNTech vaccine this week. About 47$ of people in the United States have received at least one vaccine dose, and appointments are readily available across most of the country. Some public health experts said they viewed the new mask guidance, in part, as an incentive to entice those who have not gotten shots: Getting vaccinated would mean no longer having to wear a mask.

“We have all longed for this moment,” Dr. Rochelle Walensky, director of the CDC, said at a White House news conference today. “If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic.”

What does all this mean for stores and restaurants?

The new policy seemed to catch many retailers and their workers by surprise.

Macy’s and the Gap said they were still reviewing the new guidance, while Home Depot said it had no plans to change its current rules requiring customers and workers to wear masks in its stores. Other major retailers, including Walmart, did not immediately respond to requests for comment, while officials at Target said they would keep in place mask and distancing rules while reviewing the CDC guidance.

The United Food and Commercial Workers union, representing thousands of grocery store workers, criticized the CDC for failing to consider how the new policy would affect workers who have to deal with customers who are not vaccinated. And the Retail Industry Leaders Association, a trade group, said the policy complicated matters in states that still have mask mandates in place that retailers must follow.

But how do you know whether a stranger shopping or eating next to you is vaccinated?

You probably won’t. About 36% of people in the United States are fully vaccinated, and there is no way to tell them apart from the 64% of people who are not. People who receive a vaccine are issued a white paper card, but online scammers have sold forged versions of those.

The new guidance reopened discussions of so-called vaccine passports, which would certify someone’s vaccination status. Efforts to create a more robust system of such passports have been largely derailed in the United States by concerns about privacy and backlash from Republican politicians. New York state has created its own version of a vaccine passport.

What has the CDC’s guidance been on masks all along?

At the very beginning of the pandemic, the CDC.’s position was that most ordinary people did not need to wear masks unless they were sick and coughing. At the time, there was limited understanding that the virus was airborne and could be transmitted by people who were asymptomatic, and there was also a concern that recommending masks would worsen an N95 mask shortage for health care workers.

But the CDC’s position quickly shifted. By April 2020, the CDC urged all Americans to wear a mask when they left their homes.

The guidance kept changing throughout the pandemic. For example, the agency first said that wearing masks protected others, not the wearer. By November, officials went a step further, saying masks benefited the people who wear them, in addition to those around them.

With vaccinations ramping up, the CDC began to loosen its guidance last month, advising that fully vaccinated people could remove their masks in many situations outdoors, where the virus spreads less easily.

Then Thursday, the CDC announced that the relaxed rules also applied indoors.

I’m vaccinated. So what am I supposed to do right now?

If you feel comfortable doing so, you can start going out without a mask on your face. But you might want to still keep one in your pocket.

Some local governments and businesses are likely to continue requiring masks, at least in the immediate future. And if you ride the bus or train, or are visiting a family member in a hospital or nursing home, you will still be expected to mask up.