What happened

Shares of cruise line operator Carnival Corporation (CCL -0.42%) are down 2.4% as of 3:10 p.m. EDT Friday, and it's no great mystery why: coronavirus.

So what

As CNBC reported today, a Carnival cruise ship that recently sailed out of Texas and is now docked in Belize now has a total of 27 people on board who have just tested positive for COVID-19 -- and here's the real kicker: 26 of them are crew.  

Collage showing a cruise ship, a man in a face mask and a microbe.

Image source: Getty Images.

Every single one of the 27, says Carnival, had previously been vaccinated against the novel coronavirus. Every single one of them caught the virus anyway.

Now what

In a statement, Carnival noted that all of its crew members are vaccinated, as well as "almost all of our guests." According to Carnival policy, unvaccinated guests such as "children under 12 who are not eligible for a vaccine" must show a negative COVID-19 test result at check-in, then take another test "at embarkation," and yet another within 24 hours of debarkation on cruises lasting more than four days.

Well and good. But despite these and other "stringent health protocols which included placing those who tested positive in isolation and close contacts in quarantine," more than two dozen crew members now have the virus. (On the plus side, none of the 27 passengers and crew are showing anything more than minor symptoms, according to CNBC.)

The good news is that out of 2,895 guests on board, only one seems to have caught the virus so far, so Carnival's coronavirus protocols seem to be doing a good job keeping passengers safe from each other. Now the question is how Carnival plans to keep them safe from the crew -- and if it can't do that, then how it plans to convince new customers to keep signing up for cruises.