What happened Several leading coronavirus vaccine stocks were sinking today after Moderna (NASDAQ: MRNA) announced interim efficacy results for its COVID-19 vaccine candidate mRNA-1273. Shares of Pfizer (NYSE: PFE) were down 3.9% as of 11:19 a.m. EST on Monday. Meanwhile, BioNTech (NASDAQ: BNTX) and Novavax (NASDAQ: NVAX) stocks were falling 13.2% and 10.6%, respectively. So what Investors seem to be viewing the coronavirus vaccine market as a zero-sum game where some vaccines lose when another vaccine wins. That's likely a faulty premise, though. Image source: Getty Images. Moderna's news was certainly very good. The company announced an efficacy of 94.5% for mRNA-1273 with no significant safety concerns. CEO Stephane Bancel also stated that the interim results gave the first clinical validation that the experimental vaccine could prevent severe cases of COVID-19. This efficacy was in the ballpark of the 90% or greater efficacy reported by Pfizer and BioNTech last week for their COVID-19 vaccine candidate, BNT162b2. Both mRNA-1273 and BNT162b2 use a similar approach where messenger RNA (mRNA) is engineered to spur the production of a protein identical to the spike protein on the novel coronavirus SARS-CoV-2. Moderna's vaccine could have an edge on the vaccine developed by Pfizer and BioNTech from a logistical standpoint. BNT162b2 must be stored at minus 70 degrees Celsius and can be kept at temperatures between 2 and 8 Celsius for only seven days. The new formulation of Moderna's mRNA-1273 can be refrigerated for as long as 30 days and kept at room temperature for up to 24 hours. Even with this advantage, though, both of these mRNA vaccines should be highly successful assuming they secure FDA emergency use authorizations. But what about Novavax? The company lags behind Pfizer, BioNTech, and Moderna with its plan to begin a late-stage U.S. study of experimental COVID-19 vaccine NVX-CoV2373 later this month. However, it's way too soon to dismiss Novavax's chances of success. NVX-CoV2373 won't have any of the cold-storage issues that the mRNA vaccines have. If the coronavirus vaccine candidate delivers high efficacy, look for Novavax to be a big winner, too. And because the biotech stock is a lot smaller than the other leading players, Novavax could generate the greatest gains of the group if NVX-CoV2373 delivers on its potential. Now what The next major milestone coming up for Pfizer and BioNTech is to file for FDA emergency use authorization (EUA). That filing could come any day now. Moderna will probably be hot on their heels with its EUA filing. The main thing to watch with Novavax is the initiation of its U.S. phase 3 study within a few weeks. The company also expects to announce interim results from its U.K. late-stage study of NVX-CoV2373 in early 2021. 10 stocks we like better than PfizerWhen 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 Pfizer 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 October 20, 2020 Keith Speights owns shares of Pfizer. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source