(CNN) – The U.S. Centers for Disease Control and Prevention on Thursday raised the risk level for cruises to the highest, stating that regardless of vaccination status, it should be avoided.

The agency has raised the travel risk level for cruises from Level 3 to Level 4, suggesting that the risk for Covid-19 is “very high”.

The move “reflects the increase in cases on board cruise lines since the Omicron variant was identified,” the CDC website said.

“Since the Omicron variant was identified, the number of COVID-19 cases among cruise passengers and crew reported to the CDC has increased. In addition, the number of cruise lines completing the COVID-19 case has increased. “Threshold for CDC investigations,” the agency said.

On December 30, the agency listed 91 ships in their yellow category, indicating that the number of reported Covid cases is the Examination threshold of the CDC. That is five ships more than were listed in yellow on December 28th. As of December 30, no ships were listed in red, suggesting the reported cases have reached or exceeded the threshold for investigation.

Three ships were listed in orange on Dec. 30, suggesting the reported cases are below the CDC’s investigation threshold. Sixteen ships were listed as green, which means no cases of Covid-19 have been reported on the ships.

Green, orange, yellow and red labels indicate a ship’s Covid situation from the best to the worst. A gray label is reserved for ships that the CDC has not checked for Covid security.

Decision is “confusing”, says industry association

Cruise Lines International Association, a trade association, expressed disappointment with the CDC’s increased risk level.

“The CDC’s decision to raise the level of cruise travel is particularly confusing when you consider that the cases recorded on cruise lines consistently represent a very small minority of the total population on board – far fewer than on land – and the majority of these cases are asymptomatic or asymptomatic are mild and have little or no impact on medical resources on board or on land, “CLIA said in a statement.

The association said that “cruise ships offer a tightly controlled environment with science-based measures, known tests and vaccinations well above any other location or means of transport and travel, and significantly lower incidence rates than land.”

At least four ocean cruise ships were turned away from ports of call or were not allowed to disembark passengers in America this week due to Covid-19 cases on board.

A statement from the US Travel Association also indicated frustration with the advice given by the CDC.

“The US Travel Association sincerely hopes that today’s CDC consultation highlighting recreational cruising – which was conducted despite the sector’s robust health practices and high vaccination rate (95%) on board – will be brief and temporary,” said Tori Emerson Barnes . the executive vice-president of the Association for Public Affairs and Politics.

Advice if you decide to cruise anyway

As the CDC says: “Avoid cruises, regardless of vaccination status”, It recommends cruise lines to fully vaccinate and freshen up if justified. Cruise ships should get tested one to three days before and three to five days after, regardless of their vaccination status.

The unvaccinated should then go into quarantine for five full days. People on cruise lines should also wear masks in shared locations, CDC says.

Most cruise lines require that all or the vast majority of passengers and crew be vaccinated, in accordance with a CDC Conditional Sailing Order that was put in place to resume cruise operations more than a year after the industry shut down earlier in the year Pandemic.

Many cruise lines also require pre-departure testing, regardless of vaccination status.

A few lines including Royal Caribbean, require all passengers 2 years and older to be masked in indoor public areas, except when actively eating and drinking.

Before coronavirus variants led to a surge in breakthrough cases among the vaccinated, some lines of vaccinated passengers did not require masks in areas reserved for vaccinated guests.

CNN’s Jason Hanna contributed to this report.

Above: The Seven Seas Mariner cruise ship passes the Panama Canal on December 23 after being prevented from docking by local authorities in Cartagena, Colombia. (Reuters / Erick Marciscano)