What happened

Shares of the clinical-stage vaccine-maker Novavax (NASDAQ:NVAX) gained as much as 18.2% today on sky-high volume. This noteworthy uptick was sparked by the anticipation surrounding the company's clinical update for its high-value respiratory syncytial virus (RSV) vaccine program scheduled for the close of trading today. Throughout the course of the session, however, the biotech's stock cooled off significantly, ultimately ending the day up only 2%. 

An elderly man receives an injection from a doctor.

Image source: Getty Images.

So what

Despite a slew of updates that included a positive top-line data readout from its latest mid-stage trial of the RSV vaccine candidate in older adults, the company didn't deliver any Earth-shattering news to truly warrant a hefty spike in its share price. In fact, Novavax announced that it would commence yet another mid-stage trial in older adults in 2018. That's certainly a letdown, as investors were surely hoping to hear that a pivotal-stage trial was close at hand.  

Now what

Perhaps the key takeaway, and the one clear bright spot from today's update, is that Novavax reported that the two-dose regimens of the vaccine "significantly increased immune responses and suggests two doses of the RSV F Vaccine with adjuvant may augment durability of the immune response to the vaccine." That's definitely a positive development, given the vaccine's abysmal late-stage results in elderly adults last year. 

Novavax is going to eventually be forced to raise additional funds to carry out its plan to execute another costly mid-stage RSV trial in older adults. This decision to forgo a pivotal-stage trial also significantly delays the possibility of a regulatory filing for this indication. As such, it's not surprising that the market is reacting rather poorly to this series of clinical updates -- with Novavax's shares responding by dropping by over 11% in after-hours trading. 

George Budwell has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.