If you had bought shares of Moderna (NASDAQ:MRNA) in January 2020, you would be sitting pretty right now. Thanks to its coronavirus-related efforts, shares of the biotech company are up by 524% over the past 12 months, compared to gains of 15.5% for the S&P 500. But unless you have a time machine, investing in Moderna before it rallied by more than 500% is no longer an option.

For investors who missed this opportunity, it is worth wondering if Moderna can produce similar -- or even juicier -- gains moving forward. Let's look a bit closer at the vaccine maker's prospects and figure out whether it has enough growth left in the tank to turn a relatively modest amount of money into a million dollars (or more). 

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The runner-up of the COVID-19 vaccine race

After months of developing its vaccine, mRNA-1273, at a frenetic pace, Moderna earned its coveted emergency use authorization (EUA) from the U.S. Food and Drug Administration (FDA) on Dec. 18. The biotech wasn't the first to achieve this feat, but it was a close second, right behind the pair of Pfizer and BioNTech, whose vaccine earned the FDA's approval on Dec. 11. Now that mRNA-1273 is being administered to thousands of at-risk people, how much can the company generate in revenue?

According to Bernstein analyst Ronny Gal, the coronavirus vaccine market will be worth $40 billion this year alone. It is always wise to take such estimates with a grain of salt, but there is no denying that this market -- which truly spans the globe -- will be huge. And Moderna looks likely to be one of its main beneficiaries, as things stand. In a phase 3 clinical trial, the company's vaccine was 94.1% effective at preventing COVID-19 and 100% effective at preventing severe cases of the disease.

The efficacy of Pfizer's candidate was comparable to Moderna's, but other companies in this race are falling behind these two, at least for now. 

Dollar bills raining on a woman.

Image source: Getty Images.

Johnson & Johnson and Novavax have yet to release the results from their phase 3 clinical studies for their respective candidates. It is worth noting that Johnson & Johnson's vaccine could still make huge waves in the market since it is a single-dose vaccine. Most people would rather receive one dose rather than two, and for this reason, many customers would flock to Johnson & Johnson's candidate if it proves effective.

But even assuming Johnson & Johnson's candidate is as effective as Moderna's, there is more than enough room in this market for three (or more) companies. Gal projects that Moderna will generate $13.5 billion from sales of its vaccine this year, which isn't bad for a company that did not have a single product on the market last year.

Some of Moderna's success in this space seems already baked into its stock price: The company has a market cap of $52.36 billion, which is a bit too high for a biotech that just launched its first product on the market. But the company's forward price-to-sales (P/S) ratio of 5.44 indicates that it still has some room to grow. For comparison, Johnson & Johnson's PS ratio is 4.89. In short, Moderna will likely continue to profit from its coronavirus-related efforts, and investors still have time to get in on the action.

Beyond the pandemic 

Moderna has over two dozen products in its pipeline. The company is looking to develop vaccines for infectious diseases with a high unmet need. According to Moderna, the vaccine market was worth $35 billion in 2019, and vaccines provide "the best return on each healthcare dollar invested." Of the more than 80 new viruses discovered over the past 40 years, only 4% have vaccines approved and available in the U.S. Most of Moderna's vaccine candidates utilize messenger RNA (mRNA) technology. 

That's why the approval of mRNA-1273 (and of Pfizer's vaccine) was such a big deal: Until just a month (or so) ago, no mRNA vaccine had ever received the green light from the FDA. With this victory under its belt, Moderna will now move forward with its project to develop mRNA vaccines for a host of other diseases. The biotech is looking to develop vaccines for the Zika virus, HIV, and several types of cancer. Importantly, other than mRNA-1273, none of Moderna's candidates have ever made it to a phase 3 clinical trial. In other words, there is a very long road ahead for these candidates. 

A millionaire-maker stock?

Moderna's short-term prospects look bright, as the company will benefit immensely from its COVID-19 vaccine. And although this success is already somewhat factored in its share price, I expect its stock to continue climbing this year. Moderna will use the capital it will earn thanks to mRNA-1273 to fund future projects. With $3.97 billion in cash and cash equivalents as of Sept. 30, 2020, and with more money coming in thanks to its new vaccine, it is unlikely that Moderna will resort to dilutive forms of financing anytime soon, which is good news for shareholders.

But the company's long-term plan, although very intriguing, is still too far from bearing fruit. Too much can go wrong for Moderna's pipeline candidates, most of which are still early in their development phases. For that reason, I think there are too many risks and uncertainties surrounding Moderna for it to be considered a millionaire-maker stock. But the biotech is still worth serious consideration by investors with an above-average tolerance for risk.

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.