Shares of Moderna (NASDAQ:MRNA) have soared more than 300% since the beginning of the year. And much of that gain has happened over the past two months. Earlier this year, investors watched Moderna become profitable after one full quarter of coronavirus vaccine sales. Now, they're betting on the potential authorizations of a booster shot and the vaccine's use by younger age groups.

The picture ahead looks bright for Moderna. But if you haven't yet bought shares of this innovative biotech company, today's share price might be scaring you off. After the gains, is it too late to get in on the Moderna growth story? Let's take a close look.

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Moderna and Pfizer vaccine contracts

First, a little background. Moderna and rival Pfizer are the top two sellers of coronavirus vaccines in the U.S. They've each signed contracts for 500 million doses to be delivered through the first quarter of next year. Meanwhile, the Moderna vaccine and Pfizer vaccine have fully vaccinated 67 million and 99 million Americans, respectively. The companies also have signed major deals with other countries worldwide.

Now let's focus on Moderna's financials. The vaccine, the company's very first commercialized product, generated $1.2 billion in profit during its first full quarter on the market. Considering current orders, the biotech expects the vaccine to bring in $20 billion in revenue this year. It owns full rights to the vaccine so it doesn't have to share profits with a partner.

Beyond profit and revenue, another plus is Moderna's cash level. The company has built up a whopping $15 billion in cash. This is great because it means it has funds to support its hefty pipeline. But more about the pipeline later.

So now the big question is: Will Moderna generate billions in recurrent revenue from the coronavirus vaccine? It's possible. Experts say the coronavirus is here to stay. And considering the length and depth of the pandemic, governments probably will be proactive about ordering plenty of vaccine doses for their citizens.

Stéphane Bancel's prediction

CEO Stéphane Bancel said earlier this year that market need could be greater next year. He's right. That's because by next year, regulators might expand use of the vaccine to teens and children. And boosters also could be part of the vaccination schedule. Moderna recently requested U.S. authorization for a third shot of its vaccine (at a lower dosage) as a booster. The company also is working on strain-specific boosters.

If these authorizations come through, vaccine orders might be bigger. A booster means each person would need a total of three doses rather than just the two-dose primary series. And authorization in younger people means a broader population to vaccinate.

Of course, it's impossible to predict exactly how long vaccine revenue growth may last. But we might imagine coronavirus vaccination becoming much like the flu shot: an annual routine. If that happens, Moderna may generate significant recurrent revenue. It also is working on a combined coronavirus/flu vaccine candidate. This could be a major product down the road.

Right now, Moderna relies on the coronavirus vaccine for revenue (and profit). But another potential blockbuster could be on the horizon. The company will begin a phase 3 trial for its cytomegalovirus (CMV) vaccine candidate this year. CMV is a common virus that's most dangerous for those who are pregnant or who have weakened immune systems. There currently isn't a vaccine for it.

And Moderna has 37 programs in the pipeline; 22 are in clinical trials. Its programs use mRNA technology, the same technology that powers the coronavirus vaccine. This doesn't mean every program will be successful. But the vaccine offered us evidence this approach can indeed work in humans.

Billions of dollars in revenue

So, to sum up, Moderna has billions of dollars in revenue and profit right now. And it has many candidates that could fill up its product portfolio in the future. Of course, there's always the risk of failure for one or more programs in trials. This is a risk every biotech and pharma company faces.

Today, this amazing growth story may look costly. Moderna stock has passed Wall Street's average 12-month price forecast by more than $100 and trades at 14 times forward earnings estimates. That doesn't seem excessive, but the multiple is up from less than 4 earlier this year.

Is it too late to buy Moderna shares? If you're ready to hang on to them for the long term, they are still a buy today. But I would expect gains to slow at some point. So you may not make as much on the investment as those who bought before the pandemic and sold at the end of last year, for example. Those investors, though, were rewarded for taking a big risk. Early in the pandemic, we didn't know whether Moderna's vaccine candidate would be successful.

Today, risk is a lot lower. Profit is in the billions, and we understand the potential of mRNA in vaccine development. So we're paying a higher price to join in the second chapter of this exciting adventure. But it's very possible we're still at the beginning of the Moderna story.

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.