Novavax jumps on positive flu vaccine results, while Acadia sinks on poor trials

Two weeks ago, Novavax (NVAX) shares soared some 10 percent after the small clinical-stage biotechnology company announced positive preclinical results for its new vaccine against H1N1 influenza. Shares jumped again today -- this time about 15 percent by late-afternoon trading -- after the vaccine maker announced positive results for its seasonal flu vaccine candidate in a mid-stage, or Phase II, trial. Shares reached a three-year high.

While media attention has quieted regarding H1N1, or swine flu, officials expect the outbreak, declared a pandemic by the WHO, to intensify during the Northern Hemisphere's winter. The outbreak has pressured the vaccine supply for seasonal influenza, which kills between 250,000 and 500,000 people a year.