At one time, Novavax (NASDAQ: NVAX) was the most profitable coronavirus stock ever, with a mouthwatering return of 2,400% over a trailing 12 months. However, investors who didn't sell the stock at its all-time high price of $331.68 per share in February were soon out of luck. The stock declined 44% from its peak, and now rests around $180. This has left many once-excited investors wondering: What could be behind such dramatic price movements for a company developing a promising coronavirus vaccine? Image source: Getty Images. There's good news and there's bad news Novavax's coronavirus vaccine candidate, NVX-CoV2373, is on the verge of receiving regulatory approval. In clinical tests, the experimental vaccine demonstrated 96.4% efficacy against the original strain of COVID-19. Against the variant U.K. and South African strains, the vaccine candidate was 89% and 49% effective, respectively. NVX-CoV2372 was also 100% effective at preventing severe cases of COVID-19, no matter the viral strain. This year, the company expects to produce 2 billion doses of the vaccine, contingent on approval. Having an annual production capacity of 2 billion might sound like a lot at first. On a closer look, however, the problem of actual fulfillment becomes an issue. Out of that amount, only about 300 million or so have been preordered by developed nations like the U.S., Canada, Australia, New Zealand, etc, at a price of $16 per dose. That's about $4.8 billion in revenue for a company with a market cap of $14 billion, giving the stock a price-to-sales (P/S) ratio of just 2.9. Not bad, right? Unfortunately, Novavax is having trouble turning a profit after those initial lucrative preorders. For starters, it's donating up to 1.1 billion doses of its experimental vaccine to developing nations. Secondly, the company is now delaying a 200 million-dose supply agreement with the EU due to a U.S. export ban on the vaccine's raw materials. Novavax doesn't have any manufacturing capacity on its own. Instead, it contracts eight vaccine producers around the world to assemble NVX-CoV2373. The largest of these is the Serum Institute of India, which promises to make over 1 billion doses of Novavax's vaccine candidate each year. Nevertheless, it doesn't have the actual biologics to make coronavirus vaccines and must first import them from the U.S. Given the not surprising "America First" focus of the Biden administration regarding such vaccines, it's likely that Novavax's supply will be delayed until July. That brings up another problem. By now, most developed nations have secured vaccine supply agreements from competitors such as AstraZeneca, Pfizer, BioNTech, CureVac, Johnson & Johnson, and Moderna, ranging from 2 to 9 doses per capita. In other words, the coronavirus vaccine market has mostly been maxed out by the governments that can pay. If there are any leftover doses after vaccinations are complete, they would be given to third-world countries free of charge or at no profit. At the end of the day, Novavax is largely a one-trick pony without much to fall back on other than NVX-CoV2373. While it does have its experimental NanoFlu influenza vaccine pending regulatory approval, it's just another candidate in a hypercompetitive market. In clinical trials, NanoFlu did a 10% to 20% better job immunizing patients against the flu than those currently on the market. The only issue? There are many flu vaccines available, all eyeing a meager $6.5 billion global market. NVAX data by YCharts What's the verdict? Overall, the golden time to make millions off Novavax stock has probably come and gone. Investors should be aware that the coronavirus vaccine market is incredibly saturated, and Novavax may not make more than a one-time cash flow of $5 billion off its venture. When the company's expected revenue falls off a cliff after the pandemic subsides, investors will be better off looking for other alternatives in the biotech sector. 10 stocks we like better than NovavaxWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Novavax wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of February 24, 2021 Zhiyuan Sun owns shares of Pfizer. The Motley Fool recommends Johnson & Johnson and Moderna Inc. The Motley Fool has a disclosure policy.Source