After running into some manufacturing issues, Novavax (NASDAQ: NVAX) is finally starting a phase 3 clinical trial for its coronavirus vaccine, NVX-CoV2373, in the U.S. and Mexico. The study, dubbed Prevent-19, will enroll 30,000 participants at 115 sites. The biotech trails Moderna (NASDAQ: MRNA), BioNTech (NASDAQ: BNTX), and Pfizer (NYSE: PFE), which have already gotten their coronavirus vaccines authorized by the Food and Drug Administration. Unlike those mRNA-based vaccines, NVX-CoV2373 is a protein from the novel coronavirus put on the outside of a nanoparticle. Image source: Getty Images. Novavax is shooting to have at least 25% of the participants be 65 or older. To encourage people to join the study, Novavax will give the vaccine to two-thirds of the participants instead of half of them, as other vaccine makers have done. Nevertheless it may still be hard to convince people currently eligible to receive the Moderna or the BioNTech/Pfizer vaccine to join a study when there's still a one-in-three chance of getting a placebo. Fortunately, Novavax also has a 15,000-participant phase 3 clinical trial in the U.K. that completed enrollment last month, so even if the older age group ends up being underrepresented in the U.S. study, it'll have some data on whether the vaccine can protect older adults. While Novavax is clearly late to the party, NVX-CoV2373 could still capture some market share if the vaccine is as effective, especially in rural areas, because it can be stored in a refrigerator. Moderna's vaccine needs to be frozen and BioNTech and Pfizer's vaccine has to be kept at ultra-cold temperatures. 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 November 20, 2020 Brian Orelli, PhD and The Motley Fool have no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source