Guidance issued Friday by the CDC gives Hawaii the green light to modify the program that lets arriving travelers avoid a 10-day quarantine by showing proof of full vaccination, the program’s author said on Friday.

But key details, including how to verify that the travelers have been vaccinated, still must be worked out, Lt. Gov. Josh Green said. Still, Green said, the announcement marks another step toward reopening Hawaii’s key tourism industry.

The Centers for Disease Control and Prevention said that “people who are fully vaccinated with an FDA-authorized vaccine can travel safely within the United States” and “do not need to get tested before or after travel unless their destination requires it.”

“Fully vaccinated travelers do not need to self-quarantine,” it added.

Hawaii’s current policy requires people arriving from out of state and traveling between islands to quarantine for 10 days upon arriving at their destination, a policy consistent with the previous CDC guidance. However, under the so-called “Safe Travels” program, implemented by Green, travelers can sidestep the quarantine by getting a negative COVID-19 test within three days of departure.

Safe Travels has brought tourism back to Hawaii significantly, with arrivals of more than 15,000 passengers on some days, which is about half of levels before COVID-19 shut down the state’s key industry last year.

Still, industry executives believe more people would come if they didn’t have to get the COVID-19 test, which must be a specific test administered by one of several facilities deemed “trusted partners,” including pharmacies like CVS.

Allowing people to travel with proof of vaccination would make it easier, for both visitors and returning residents, who are subject to the quarantine and testing policies, tourism industry executives say.

Green said the CDC guidance gives him and Maj. Gen. Kenneth Hara, who heads the Hawaii Emergency Management Agency, the ability to move forward modifying Safe Travels to include vaccinated travelers “as soon as validation, processing and enforcement issues (are) worked out.”

One key tool, which Hawaii and other locales are working to develop, is an electronic document, often called a “vaccine passport,” that would show proof of vaccination. But it’s not clear when the passport would be available in Hawaii.

Gov. David Ige’s spokeswoman, Cindy McMillan, declined to comment on Friday. However, Ige has signaled Hawaii will follow CDC guidance when implementing a passport.

In a Feb. 22 interview on the Honolulu Star-Advertiser’s Spotlight program, for instance, Ige said that setting a timeline for implementing a vaccine passport couldn’t be done because the CDC had not provided guidance on how to treat vaccinated individuals who travel.

He said Hawaii couldn’t make any changes to the Safe Travels program until more information came from the CDC.

In another Spotlight interview on March 24, Ige said that he would be in talks with the White House regarding the passport this week.

“Obviously it is more future, we need to get more people vaccinated, definitely as we get into the summer,” he said. “For Hawaii especially, we want to be able to understand what risks vaccinated people might present and how we might be able to bring travelers who have been vaccinated.”

Hawaiian Airlines, one of the state’s largest employers and one hardest hit by COVID-19, said it was pleased to see the CDC’s guidance and was “hopeful the state of Hawaii will update the Safe Travels program to align with these recommendations.”

“While we must all continue to take personal responsibility to protect ourselves and each other, it’s time to restore freedom of travel to allow families and friends to reconnect and generate crucial economic activity,” the carrier said in a statement.