Cruisers, be warned: The window to get a pre-cruise COVID-19 test is shrinking

Take note, cruisers: Cruise lines are starting to shorten the window of time that you have to get a COVID-19 test before sailings out of U.S. ports.

Cruise giant Carnival on Thursday announced that, effective Sept. 13, most passengers would have to show proof of a negative COVID-19 test taken no more than two days before sailings to board its vessels. That's one day less than passengers currently have to get a test.

The new policy applies to passengers who are vaccinated for COVID-19, which is most Carnival passengers at the moment. Carnival is requiring all passengers to show proof of a COVID-19 vaccine, with the exception of a small number of children under the age of 12, and teens and adults with a proven medical condition that doesn't allow them to be vaccinated.

The line has different, more-involved testing requirements for unvaccinated passengers.

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Princess Cruises on Thursday also added a requirement that passengers show proof of a negative COVID-19 test taken within two days of boarding. In Princess's case, the requirement applies to all passengers, whether vaccinated or not, and doesn't take effect until Sept. 19.

MSC Cruises followed on Friday with an updated testing policy that was similar to Carnival's new policy. Effective Sept. 13, vaccinated passengers sailing out of U.S. ports on MSC Cruises ships will have to show proof of a negative COVID-19 test taken no more than two days before sailing.

All three of the lines will accept the results of either a COVID-19 PCR or a rapid antigen test.

The new policies come just days after the U.S. Centers for Disease and Prevention (CDC) revised its rules for cruise ships sailing in U.S. waters to include a requirement that fully vaccinated passengers get a COVID-19 test no more than two days before boarding. The CDC said the test could be either a PCR test or an antigen test.

The CDC issued separate guidance for unvaccinated cruisers, saying they only could take a PCR test, which could be done up to three days before sailing. Unvaccinated passengers on sailings out of U.S. ports are subject to additional screening and testing requirements upon arrival at ships and once on board.

The new two-day window for testing could present a challenge for some cruisers who live in areas of the U.S. where slots for COVID-19 tests are becoming harder to get, something that Carnival acknowledged in a posting Thursday on the part of its website devoted to testing requirements.

The line said it was planning to add mobile testing centers at its U.S. ports to serve as a backup for passengers who are unable to get a COVID-19 test in a timely manner at home.

"We realize some of our guests are having a challenge getting a pre-cruise COVID-19 test, especially with the new two-day window established by the CDC," the line said. "We are working to set up mobile testing sites at all our embarkation homeports to conduct a rapid test the day before or day of your departure."

Carnival said it still was "working out the details" of such a plan and passengers should check back on its testing requirement page for more information at a later date.

Carnival said the tests at the mobile testing centers would come with a cost, to be set by the outside companies that will be handing the testing. Passengers will have to pay for the testing at the time of service, as the companies will not be accepting health insurance, Carnival said. But passengers may be able to submit the cost to their insurance companies later.

"You should consider this as a backup alternative should you not be able to make arrangements," the line added.

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