The past two years have been incredible for Moderna (NASDAQ:MRNA) -- and its investors. Shares of the biotech company surged more than 430% in 2020. And they're heading for an increase of more than 180% this year. That's because Moderna brought a coronavirus vaccine to market and became one of the leading players in the field. The company went from zero product revenue and a net loss to billions in revenue and profit in just a few months.

So, what's ahead for this vaccine giant? Well, gains next year may not come as easily as they did over the past two years. Positive and negative factors will compete to determine which direction Moderna stock takes in 2022. I'm focused on two in particular. Let's take a look at one green flag for Moderna in the coming year -- and one red flag.

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Image source: Getty Images.

The green flag

As strange as this may sound, the green flag is actually the omicron variant. I'll explain. Prior to the emergence of omicron, investors were already thinking about the post-pandemic world -- and worrying that vaccine sales would sink like a stone, even though experts predicted the coronavirus would stick around.

Today, omicron is proof that experts were right. The virus isn't going away any time soon. And that means the world will need protection beyond the primary series of vaccines and a booster. In fact, the world might even need vaccine updates periodically as new variants emerge.

Moderna is set to handle this. The company is testing two booster candidates that cover a range of coronavirus mutations. These candidates could possibly work for several strains. Moderna is also developing a strain-specific booster to target omicron. The idea is that this sort of candidate could be quickly updated according to the newest variant to emerge.

All of this clearly could boost sales for Moderna down the road -- and spur countries to plan vaccination beyond next year. This week, Moderna announced an updated supply agreement with the U.K. for an additional 60 million doses through 2023. This includes vaccine and doses of new booster candidates if they win authorization.

The red flag

And the big red flag for Moderna in the months to come is competition. Right now, Moderna and bigger rival Pfizer have established themselves as market leaders. They've each carved out significant market share, and both can generate billions of dollars in revenue annually from vaccine sales. The Johnson & Johnson vaccine remains far behind. Concerns about efficacy and rare blood clots weighed on the J&J vaccine from the start.

But a new player may soon enter the field. And that player is called Novavax (NASDAQ:NVAX). Novavax plans on filing for authorization in the U.S. market by the end of this year. A regulatory decision may follow in a period of just a few weeks.

Novavax doesn't use cutting-edge mRNA technology like Moderna and Pfizer. Instead, Novavax uses technology that's already brought other vaccines to market -- such as the hepatitis B vaccine. That means people who have hesitated to take an mRNA vaccine due to its newness may feel more comfortable choosing Novavax.

And one other element may make competition a real issue for Moderna: Vaccine "mixing and matching." The U.S. Food and Drug Administration recently authorized this. Basically, it means that if you've had the primary series of an authorized vaccine, you can choose that brand or any other for your booster. This opens the door for Novavax -- or any other player that may reach commercialization down the road -- to take some market share from Moderna.

Will the green flag or the red flag dominate?

The coming year may determine whether Moderna stock can climb over the long term. Overall, I expect Moderna's revenue and share price to progress. Gains may not be as steep as they were in the past. It's difficult for a stock to keep up that pace forever. But I'm optimistic Moderna will continue on its way to becoming a solid long-term investment. The company has been proactive from the start of the coronavirus pandemic -- so I'm confident it can maintain its spot even if competition may be a challenge at times.

And Moderna has a strong pipeline of potential products beyond the coronavirus area. This should eventually translate into more products and revenue down the road. And that's clearly a green flag for shareholders.

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.