What happened

Shares of Norwegian Cruise Line Holdings (NCLH 1.60%), Carnival Corporation (CCL -0.11%), and Royal Caribbean Cruises (RCL 0.78%) -- the three horsemen of the cruise industry apocalypse -- stumbled lower in afternoon trading Wednesday. As of 12:30 p.m. EDT, Norwegian stock is down 3.7%, Carnival 3.2%, and Royal Caribbean 2.2%.

So what

Why are these stocks down? Not because of any cruise industry news, certainly. In fact, the latest news out of cruise land is of the positive sort -- Carnival subsidiary Cunard announced that it has begun selling tickets for a 2022 "World Voyage" aboard the Queen Mary 2 sailing out of New York City.  

Instead, I suspect that cruise industry investors owe their woe today to news of a different sort.

Yesterday after close of trading, pharmaceutical company AstraZeneca reported that it has paused its phase 3 clinical trial of its AZD1222 COVID-19 vaccine to give it time to review safety data tied to a patient who has apparently suffered an adverse reaction.  

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

Image source: Getty Images.

Now what

Commenting on AstraZeneca's move, which was first reported in the Stat medical journal last night, J.P. Morgan yesterday urged investors not to "over-interpret the impact of this afternoon's news," saying that a single patient falling ill -- which might not be tied to the vaccine -- is no reason to panic and is likely to have only an "extremely limited" impact on the race to find a safe vaccine against the coronavirus.    

Stat, however, noted that "the finding is having an impact on other AstraZeneca vaccine trials under way — as well as on the clinical trials being conducted by other vaccine manufacturers." And J.P. Morgan itself warned that the real risk here is that news of the illness "could damage the public perception of vaccine safety."

That's the news that's of real import to cruise investors today: The sooner a vaccine is discovered, tested, and distributed, the sooner it will be safe to cruise again and the sooner the CDC can be expected to lift its broad no-sail order on cruise ships sailing from American ports. Anything that "damages the public perception of vaccine safety," however, can be expected to delay that happy day.

And this, in a nutshell, is why cruise stocks are going down today.