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What: Shares of Novavax (NASDAQ:NVAX), a biopharmaceutical company focused on developing recombinant protein nanoparticles that can be used in vaccines and as adjuvants to existing therapy, jumped as much as 18% Tuesday after the report of positive top-line data from a midstage trial involving its RSV-F protein nanoparticle vaccine in women of childbearing age.

So what: According to Nanovax's press release (link opens PDF), released after the closing bell last night, the company's respiratory syncytial virus vaccine was well-tolerated with no vaccine-related adverse events and a consistent safety profile from phase 1 into phase 2 studies. Also consistent with phase 1 data, per the press release, "women with the lowest baseline levels of RSV neutralizing antibodies had the largest increase following immunization." Significant increases in RSV-F antibody levels were also observed across all doses.

Now what: This is undoubtedly positive news for Novavax, but I would caution shareholders to remain somewhat cautious as the company's pipeline is still wet behind the ears. In addition to its RSV vaccine, it has seasonal and pandemic influenza vaccines under study, as well as a rabies vaccine in preclinical studies. All of these trials may result in success, but investors can't know that yet while the pipeline remains focused more on safety and tolerability at this stage than actual efficacy. Until we get into the meat and potatoes of late-stage trials it's best to not get too wrapped up in these early and midstage results.

Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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