What happened

Carnival (CCL 3.57%) (CUK 3.71%) shareholders trounced a surging market in November as their stock rose 46% compared to the 11% increase in the S&P 500, according to data provided by S&P Global Market Intelligence.

The rally didn't put much of dent in wider losses, though, and the cruise ship giant remains lower by over 50% so far in 2020.

A retired couple on a cruise.

Image source: Getty Images.

So what

November's rally reflected growing optimism that a COVID-19 vaccine will soon be widely available, which would allow for Carnival and its peers to resume normal operations perhaps as early as mid-2021. News that multiple effective vaccine candidates are now in production had Carnival shares jumping in concert with Royal Caribbean Cruises and Norwegian Cruise Line Holdings last month, and the broad rally has continued into early December.

Now what

There's still an almost complete global pause on sailings, and so it remains an open question when Carnival can resume packing guests onto it ships. In the meantime, the cruise leader must fund its substantial fixed costs through debt, including the additional $1.5 billion it took on last month.

Those difficult conditions warrant plenty of caution for investors hoping to buy into a rebound story for this business, which could struggle under lingering COVID-19 pressures for years even if the economy avoids slipping into a recession in 2021.