The pandemic has led to earnings and share-price gains for Moderna (MRNA 2.61%). The biotech company is one of the biggest coronavirus vaccine makers. It's generated billions of dollars through sales of that product. And those who invested in Moderna at the start of the vaccine race saw their investment climb more than 750% in less than a year.

Today, the pandemic isn't over, but we may be getting close to that point. Last week, the World Health Organization's director general said, "[T]he end is in sight." That's after the number of weekly deaths fell to its lowest since March 2020.

Investors have worried about Moderna's vaccine sales in a post-pandemic world, which is why the shares have suffered this year. Does this mean we should avoid Moderna -- or is it a great stock to own, even once the pandemic is over?

Today's Moderna

First, a quick look at how Moderna's doing right now. The company brought in $18.5 billion in vaccine revenue last year and expects to generate $21 billion this year, according to advance purchase agreements signed so far. These agreements cover Moderna's original vaccine and strain-specific booster. The company is launching the booster for the fall vaccination season. 

Let's look ahead to the post-pandemic situation. Here's one positive point: Most recently, Moderna offered us clues about sales once the pandemic is over.

Depending on pricing of the vaccine and uptake, the U.S. market could represent between $5.2 billion and $13 billion. These numbers should move higher if we add in international markets. Even if Moderna's vaccine revenue falls from today's levels, it's still likely to remain in blockbuster territory.

Experts say the coronavirus will stick around -- a lot like the flu. This means Moderna may have a steady, recurrent source of revenue. The company's messenger RNA technology allows it to quickly update vaccines with the latest strain. Moderna's plan is to produce vaccines according to the specific needs of each particular market.

Moderna may be set to carve out a multibillion-dollar spot in the post-pandemic coronavirus vaccine market.

Not just a coronavirus company

Here's a second positive point. Moderna isn't only a coronavirus vaccine maker. The company has 46 programs in development across a range of therapeutic areas. And three non-coronavirus candidates are in phase 3 trials right now including vaccine candidates for flu, respiratory syncytial virus (RSV), and cytomegalovirus (CMV).

Moderna has indicated that if all goes smoothly, the flu and RSV candidates could enter the market within the coming two to three years. So other sources of revenue may not be far off.

As for the market sizes, here's more good news. Today's flu vaccine market is worth between $5 billion and $6 billion. But Moderna says more effective vaccines could result in a bigger market -- and it's working to make that happen. Moderna says RSV vaccines for older adults is a $10 billion opportunity, and the CMV market is worth between $2 billion and $5 billion.

In a post-pandemic world, Moderna may find itself winning in other billion-dollar markets.

Is Moderna stock a smart buy?

Let's get back to our question: Is Moderna a post-pandemic buy? Considering the two positive points I mentioned above, the answer is "yes."

Today, the shares are trading at 5.2 times forward earnings estimates, which looks cheap. That's because Moderna's plans for the long-term coronavirus market and its pipeline indicate it may continue to generate billion-dollar revenue over time. And Moderna's $18.1 billion in cash -- thanks to vaccine sales -- means it has the funds needed to advance pipeline candidates.

The pandemic is still part of our daily lives, but once it's over, Moderna's earnings prospects look solid. The company has what it takes to grow revenue over time -- and that should lead the shares higher over time, too.