Cruise lines are tightening pandemic protocols as the Delta variant of COVID-19 surges globally, with Carnival Cruise Line the latest to tighten vaccine requirements.

Why it matters: Cruise ships were a coronavirus epicenter early in the pandemic, and the CDC advised last Friday that people at increased risk of severe illness from the coronavirus should avoid traveling on cruises.

What's happening: The Bahamas' government imposed an emergency order last Thursday banning ships from the country unless everyone over 12 was inoculated against the virus, effective Sept. 3.

• Royal Caribbean imposed this vaccination requirement the same day.
• Carnival announced Sunday that from Sept. 3 all guests over 12 years old on cruise lines calling on ports in the Bahamas must be fully vaccinated for COVID-19 unless they have a medical exemption.
• "Effective Aug. 28 through October, for departures from all Atlantic and Gulf homeports, only children under 12 and adults with a medical condition that prohibits their vaccination are exempt from vaccination requirements to sail," Carnival added in its statement.

For the record: The Carnival Vista saw the biggest outbreak of coronavirus cases since cruises resumed in the U.S. and Caribbean last June, with 27 people testing positive for COVID-19 after sailing out from Galveston, Texas, in late July and early August, per the New York Times.

• One of those passengers later died of the virus in an Oklahoma hospital, though Carnival spokesperson Chris Chiames said in an emailed statement to Axios that the woman "almost certainly did not contract COVID on our ship."
• Royal Caribbean saw six guests test positive for the virus on the Adventure of the Seas ship, the NYT notes.
• Both cruise companies responded by further tightening measures.

Of note: Several cruise companies are defying Florida's vaccine passports ban — notably Norwegian Cruise Line Holdings, which has filed a lawsuit challenging the order by Gov. Ron DeSantis (R).

What they're saying: "Carnival has implemented a suite of protocols that are designed to flex up as needed to adapt to the changing public health situation related to COVID-19, Chiames said.

• "We meet the standards for a vaccinated cruise as defined by the CDC, with at least 95 percent of our guests and all of our crew being vaccinated, and then implemented additional measures, as we are now requiring vaccinated guests to present both proof of vaccination and a negative COVID test at check-in. 
• "Those few guests who cannot be vaccinated are tested twice before boarding the ship, and again at debarkation.  And all guests must wear masks in the indoor areas of the ship where people gather, such as dining rooms, theaters and casinos," Chiames added.