Companies have to have Phase III trials before they can get approval. Phase I proves safety and dosing while Phase II shows it is better than a placebo and Phase III is intended to show it either works better than existing treatments or has fewer side effects. That's all after numerical models and animal studies. Since FDA essentially doubled the costs to get drug approval in the early 2000s only the most promising drug advances to Phase III. perhaps 1 in 5,000 that look good on a computer. It simply isn't worth the cost otherwise.
Currently infants at risk take palivizumab to try and prevent RSV infections or serious complications if they get it, but Novavax feels confident in its ResVax, which is nearing the end of phase 3 efficacy trials. They are also working on a flu vaccine, NanoFlu, currently in Phase II, with FDA saying it could be given an accelerated approval schedule.
If they look successful, finding money will be no problem, but they may be running out of time. The company lost almost $45 million last quarter, with revenue of just under $8 million. But RSV infections are a dangerous cause of pneumonia for infants and seniors and the company has the only vaccine in late-stage clinical trials. The company suggests they are confident of success and said they intend to submit applications to the FDA in the first quarter of 2020.