Cruise companies can speed up their restarts in U.S. waters if they guarantee most crew and passengers are vaccinated against COVID-19, the U.S. Centers for Disease Control and Prevention said in a letter to companies Wednesday night obtained by the Herald — meaning passenger cruises could restart from South Florida in July. 

If ships can certify that 98% of their crew and 95% of their passengers are vaccinated, they won’t need to do test cruises before restarting passenger operations, the letter said. The CDC estimates that passengers could be boarding cruise ships in U.S. waters as soon as mid-July depending on how quickly cruise companies meet the agency’s requirements.

The change to the restart timeline comes after a month of twice-weekly meetings between the CDC’s maritime team and the cruise industry and ports.

CEO of Royal Caribbean International Michael Bayley said the quicker timeline for vaccinated cruises is a positive development.

“The mood of Royal Caribbean last night and late into the night was simply positive that all of this dialogue that was constructive resulted in clearly being heard,” he said on a company earnings call Thursday. “The vaccines are the major foundational game changing element of this.”

In its letter to cruise companies Wednesday, the CDC also changed testing and quarantine requirements for passengers and crew. Once U.S. cruises restart, fully vaccinated people will be required to take a rapid antigen test — whose results are usually available within in a few hours — before boarding instead of a PCR test, whose results can take days. Passengers who require a post-cruise quarantine period will be able to quarantine at their home if they live within driving distance of the ship.

Passengers have not boarded ocean cruises in U.S. waters since March 2020 after COVID-19 outbreaks and deaths on multiple ships.

The CDC’s conditional sail order, first issued in October, lays out benchmarks cruise companies must meet before they can welcome passengers back. The first phase required companies to ramp up their onboard COVID-19 testing capabilities to be able to test crew members for the virus weekly and report results to the CDC. 

Instructions for the second phase, published in early April, require companies to secure agreements with U.S. ports and local health authorities in the places they plan to visit and develop vaccination plans for passengers and crew.

Some cruise companies have already pledged to require all of their passengers and crew for U.S. cruises be fully vaccinated, including Virgin Voyages and Norwegian Cruise Line Holdings. Cruise companies are already enforcing the 100% vaccine rule for upcoming cruises in other countries, including the United Kingdom and Israel.