What happened

Carnival Corporation (CCL -0.62%) stock had a good session yesterday, rising along with the rest of the cruise line industry and ending 5.5% higher on hopes that a new anti-COVID-19 pill, monoclonal antibody treatments, and a third round of booster shots from Pfizer might be enough to put the coronavirus pandemic to bed.

Today, however, Carnival stock is trending lower again -- down 2% as of 11:15 a.m. ET -- as are both of its publicly traded peers.

Two people wearing masks on a cruise ship.

Image source: Getty Images.

So what

What's ailing Carnival this time? Call it "pandemic fatigue." No sooner had Pfizer uttered its encouraging words about the prospects for a third shot of vaccine protecting travelers from omicron than CNBC reported today that the drugmaker is talking up a fourth round of shots for Americans.

While sticking with his assertion that a third dose of vaccine might make patients "well covered" and protected from omicron, Pfizer CEO Albert Bourla questioned "for how long" that protection might last. Ultimately, he concluded his statement by saying, "I think we will need a fourth dose" -- and maybe within 12 months of taking the third dose.  

Now what

Is it just me, or is anyone else getting tired of this seemingly never-ending series of variants and vaccine boosters going on and on and on? Because I have to wonder if it's starting to feel like a drag for people contemplating booking an ocean cruise, or an airline flight, or a stay in a hotel. And the more convinced travelers get that this is never going to end, the less enthusiastic they're likely to be about going online to seek good deals for a vacation.

Of course, it's always possible that as the coronavirus pandemic evolves into an endemic illness, folks may just decide to live with the risk -- that whatever protections we've got are probably enough, they're tired of postponing their vacations, and so they're just going to stop paying attention to what pharmaceutical CEOs tell them. That would probably be good news for Carnival stock.

For now, though, I think investors are just tired of the relentless march of bad news -- and that's why shares of Carnival are going down again today.