The CDC wants cruise ships arriving in and leaving the U.S. to have high Covid-19 vaccination rates, but that's not required, according to a new set of guidelines for cruise ships unveiled on Wednesday.

According to the CDC's guidance in its section of frequently asked questions, a threshold cruise ship operators can consider is the number of passengers and crew who are up to date with their Covid-19 vaccine.

The CDC used to classify ships based on their vaccination rate, such as by "standard of excellence" or "not highly vaccination" Potential passengers were told the percentage of their fellow travelers who would be vaccine free.

The Covid-19 Program for Cruise Ships ended on July 18th.

Some of the new guidance is not required. It is recommended by the CDC that cruise lines only require pre-embarkation testing within one day of embarkation, but it is also recommended that lines only require testing within three days of departure.

  • Related: Azamara drops precruise Covid testing

Some cruise companies have said that they will stop pre-embarkation testing in the next few weeks. The U.S. was included in the testing until the CDC discontinued the Covid-19 program.

In the event of sustained transmission of Covid, ships are encouraged to suspend operations. To identify the severity of a Covid outbreak, the CDC recommends using a measure called the attack rate.

The cumulative number of passenger cases in the last seven days is used to calculate the rate. If the attack rate for passengers or crew is greater than or equal to 10% at least once weekly over three consecutive weeks, it's time to suspend operations.

The CDC requires cruise lines to submit data on confirmed Covid-19 cases. Individual cases of Covid-19 are not required of ships that do not submit a daily form. Travelers should contact their cruise line if they want to learn more about Covid-19 cases.

The CDC advised travelers with a medical condition or who take medication that compromises their immune system to talk to their healthcare provider if they want to take a cruise.

If the cruise line doesn't require it, travelers should check directly with their line about Covid testing andVaccination protocols before traveling.