Carnival (NYSE:CCL) (NYSE:CUK) shares sank 57% in 2020 as the coronavirus pandemic halted sailings throughout the world. While managing the pandemic, the company has burned through hundreds of millions of dollars a month to maintain ships and cover its expenses, and it has raised $19 billion through various transactions to help weather the economic storm it's in. Carnival's Costa and AIDA brand ships have resumed limited operations in recent months but then paused again as coronavirus cases rose in their European home markets.

There is some bright news on the horizon. Countries are beginning to immunize their citizens, using recently approved COVID-19 vaccines. And the Centers for Disease Control and Prevention (CDC) last fall issued a Framework for Conditional Sailing Order -- guidelines to bring ships and their passengers back into operation.

As the situation begins to improve, is now the time to buy Carnival shares? Let's take a closer look.

Two friends stand on a cruise ship's deck and smile as they point to something in the distance.

Image source: Getty Images.

Vaccinations and the CDC's latest order

At the moment, government regulatory agencies have granted emergency authorization to administer the Pfizer and Moderna vaccines in the U.S., the European Union, and several other countries. Mass vaccinations are key to slowing the spread of the virus and helping convince the general public it is safe to once again move about freely. That's good news for Carnival. The CDC's latest order is also good news. It opens the door to the potential for cruising in the near future. This is an improvement from the CDC's No Sail Order, which was issued last spring.

Carnival management, in a fourth-quarter earnings conference call, said the cruise line hasn't yet set a date for test cruises -- a requirement under the new CDC order. Test cruises involve sailing with volunteer passengers to confirm the efficacy of new health and safety measures aboard ship. Carnival has started to bring ships back to the U.S., an essential step prior to launching a test. And Carnival said it now is waiting for CDC guidance regarding the timing of these tests.

Meanwhile, Carnival has prepared itself to withstand the worst-case scenario. CEO Arnold W. Donald said the company has $9.5 billion in cash and can sustain itself this year even in "a zero-revenue environment."

Carnival also has made efforts that will help its earnings into the future. The company has sped up the optimization of its fleet with a plan to dispose of 19 ships. It's already removed 15 of them. These ships represented only 3% of operating income in 2019. The move will cut overall unit costs by 2% and unit fuel costs by 1%. The company also has delayed the delivery of some newer ships.

Carnival said it hopes to have all of its remaining ships back in service by the end of 2021. Of course, this will depend on the pandemic. If vaccination efforts take longer than planned and the crisis lingers, Carnival might not meet that goal.

Investor takeaway

So what does this mean for investors? It's too early to say if Carnival will indeed bring all of its ships back to the seas this year. But even if it doesn't, I think Carnival's rebound is just a matter of time.

Company management predicts Carnival will benefit from pent-up demand. Carnival said cumulative advanced bookings for the first half of 2022 have surpassed those of the same time period in 2019. Another positive sign: About 60% of bookings made during the most recent quarter for sailings in the 2021 fiscal year were new bookings and not re-bookings from canceled cruises. This shows people aren't booking cruises just to use up pre-paid vouchers.

Still, Carnival remains a risky stock because we don't know when the coronavirus pandemic will ease and therefore when the ships will sail again. If things improve quickly, Carnival's shares may rebound this year. If they don't, investors will have to be patient. We'll also have to hope that Carnival can continue to manage its cash levels and control cash-burn rates. Those are key points to watch in upcoming earnings reports.

So, yes, buying shares of Carnival before they go back up is a good idea. But buying them right now? That's only a good idea if you're an aggressive investor who can handle a lot of risk and is willing to be a little patient.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.