The Centers for Disease Control and Prevention has amended its guidance for fully-vaccinated Americans, no longer recommending masks indoors or outdoors, including in crowds, CDC Director Rochelle Walensky announced at a White House briefing Thursday.

“If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic,” Walensky said, announcing the sweeping change. “Anyone who is fully vaccinated can participate in indoor and outdoor activities, large or small, without wearing a mask or physical distancing.”

The new recommendation, which carves out exceptions for buses, planes, trains, hospitals, prisons and homeless shelters, will have significant implications for schools and businesses as the country begins to reopen.

“We have all longed for this moment when we can get back to some sense of normalcy,” Walensky said.

The new recommendation is an about-face from guidance issued just 16 days earlier in which the CDC suggested masks should still be used indoors or in crowds even if people are fully immunized, which the CDC defines as two weeks after the final shot.

In announcing the decision Thursday, the CDC pointed to additional data from the last few weeks that show the vaccines work in the real world, stand up to the variants and make it unlikely vaccinated people can transmit the virus.

While states will still have the choice to implement their own guidelines — nearly half of all states still had some sort of state-wide mask mandate in place as of Thursday morning — the new guidance will have immediate implications for offices, schools and public-facing businesses.

At the same time, mask enforcement for non-vaccinated people will be challenging and is likely to re-up the discussion on vaccine passports, which some states have banned.

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