The Centers for Disease Control and Prevention announced new masking guidelines Thursday that carry welcome words: Fully vaccinated Americans, for the most part, no longer need to wear masks indoors.

The agency also said fully vaccinated people don’t have to wear masks outdoors, even in crowded spaces. 

There are still some exceptions. But the announcement represents a quantum shift in recommendations and a major loosening of the mask restrictions that Americans have had to live with since COVID-19 became a major part of U.S. life 15 months ago.

“Anyone who is fully vaccinated can participate in indoor and outdoor activities, large or small, without wearing a mask or physical distancing,” CDC Director Dr. Rochelle Walensky said during a White House briefing. “If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic.”

Health experts say the new CDC guidelines may encourage more people to get vaccinated by enticing them with tangible benefits, but it may also add to the confusion of mask etiquette in the United States.

Here are some questions that remain unanswered:  

What places do I still need to wear a mask? 

CDC guidelines say fully vaccinated people must still wear a mask in health care settings, transportation hubs such as airports and stations, and public transportation. That includes planes, buses and trains traveling into, within or outside of the U.S. as part of a federal mask mandate that was extended to Sept. 13. 

The agency also said fully vaccinated people must wear a mask or socially distance in places required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance.

It means fully vaccinated people may still need to wear a mask depending on where they live and where they go. Some business owners may follow CDC guidelines, but others may be more reluctant to lift their own rules on masking.

How is this going to be enforced? 

If schools, offices, or local businesses plan to implement CDC guidelines and allow fully vaccinated people to remove their masks indoors, how will they do that?

It’s impossible to know for sure if someone is fully vaccinated or unvaccinated without asking to look at their vaccination card.

“We’re creating a situation where private companies or individuals are responsible for their business and find(ing) out if people are vaccinated – if they’re even going to be enforcing that,” said Rachael Piltch-Loeb, associate research scientist at New York University School of Global Public Health and a preparedness fellow at Harvard T.H. Chan School of Public Health.