Just days before the cruise industry is set to sail in U.S. waters, the Centers for Disease Control and Prevention has eased its recommendations for passengers traveling onboard cruise ships this summer slightly.

The agency is only recommending cruise travel to passengers that are fully vaccinated against COVID-19. The vaccine requirement is in line with cruise line requirements that will take place from U.S. ports, unless they originate in Florida.

Cruises departing from a Florida port will not require passengers to show proof of vaccination. Other U.S. originating cruises require 95% of passengers to be fully vaccinated to board ships for sailing per the CDC’s Framework for Conditional Sailing Order.

The CDC said it is recommending people who are not fully vaccinated avoid cruise ships and river cruises worldwide.

The CDC said in its guidelines, “Since the virus spreads more easily between people in close quarters aboard ships, the chance of getting COVID-19 on cruise ships is high. It is especially important that people who are not fully vaccinated with an increased risk of severe illness avoid travel on cruise ships, including river cruises.”

It continued by saying, “Cruise passengers who are not fully vaccinated are more likely to get COVID-19, which spreads person-to-person, and outbreaks of COVID-19 have been reported on cruise ships.”

Cruise ships were considered superspreaders at the height of the COVID crisis, where thousands of cases of the virus were being reported among passengers and crewmembers.

The cruise industry was shut down for 15 months due to the COVID pandemic and is just now resuming operations, with the first U.S. sailing starting Sunday with a Royal Caribbean test cruise that was approved by the CDC in May.

In the recommendations from the CDC, the agency is suggesting that passengers get tested for COVID-19 one to three days before their trip and three to five days after they return from their cruise. The agency also said that passengers that are not fully vaccinated should self-quarantine for seven days after a cruise even if they test negative for the virus.

The new CDC recommendations come after Royal Caribbean canceled the first sailing of its Odyssey of the Seas ship after eight vaccinated crew members tested positive for the virus and after an earlier sailing when two passengers also tested positive for the virus at the end of a St. Maarten cruise onboard a Celebrity Millennium ship.

In light of the new recommendations, the CDC has lowered the risk of traveling on a cruise ship to “high” a slight decrease from the previous “very high” risk warning.

Cruise ship
A cruise ship is seen here.