 Shares of Novavax Inc. NVAX, 6.69 were down 3.4 in premarket trading on Thursday after the company said its combination COVID-19 vaccine and flu shot candidate generated an immune response in a Phase 12 clinical trial. Novavax also said that the safety and tolerability of the combination vaccine was consistent with getting a standalone COVID-19 vaccine or flu shot, and it plans to begin a confirmatory Phase 2 clinical trial this year. 