What happened

Shares of Novavax (NVAX -5.11%), a clinical-stage biotech developing new vaccines, gained 17.6% in November, according to data from S&P Global Market Intelligence. Investors looking forward to upcoming clinical trial results for two experimental vaccines gave the stock a push in the right direction.

So what 

Respiratory syncytial virus (RSV) sends more infants to U.S. hospitals in their first months than any other disease, and there aren't any effective vaccines that can prevent them from catching it. Novavax will report top-line results from a pivotal maternal vaccination study with its RSV candidate, ResVax, in the first quarter of 2019. Around the same time, the company should also be ready to show investors mid-stage results from its next-generation flu vaccine, NanoFlu. 

A woman's finger draws an upward-sloping line, with an arrow at the end.

Image source: Getty Images.

Novavax had been beaten down following a secondary share offering, and investors are increasingly hopeful that at least one of the company's vaccines will score some points. Recent flu and RSV seasons in the U.S. have been much stronger than during 2015 and 2016, when ResVax failed to lower RSV infection rates compared with a placebo among older adults.

Now what

We'll soon find out if ResVax's previous flop was simply a case of poor timing or a more serious problem with the company's proprietary vaccine development platform. In May, Novavax finished enrolling around 4,600 expectant mothers. If the children of vaccinated mothers presented fewer RSV symptoms than infants whose mothers were given a placebo, this stock will soar.

Novavax finished September with a $146 million cash balance after burning through $135 million during the first nine months of the year, which means investors will need to remain braced for another dilutive share offering in the quarters ahead. If RSV proves to be too ambitious a target for Novavax, raising enough capital to advance NanoFlu could become impossible.