The transition comes about two weeks after the agency bumped cruise travel up to the highest-risk level in its regularly updated travel notices, advising travelers to avoid cruises regardless of vaccination status.
As of January 12, all of the ships carrying passengers that are currently monitored under the agency's cruise ship color status system were listed as yellow, indicating that the volume of COVID-19 cases reported has met the CDC's threshold for investigation.
"I think the conditional sail order and the fact that the industry has stepped up and is now interested in doing and exceeding, as you know, the compliance with the sail order without the order even necessarily needing to be in place is a real testimony to how well that has worked," said CDC Director Dr. Rochelle Walensky.
The voluntary program only applies to ships operating in US waters and sailing on international itineraries. Cruise ships sailing only in US waters that choose not to participate will not be included on the color status list.