** Shares of COVID-19 vaccine-maker Moderna MRNA.O rise 2.5% to $53.44 in morning trade

** U.S. FDA staff say data demonstrating a strong immune response to MRNA's flu shot may support effectiveness in adults 65 years and older

** The shot, mFlusiva, also showed superior relative vaccine efficacy versus a standard-dose flu vaccine in adults 50 to 64 years old, they say in briefing documents published ahead of the regulator's advisory meeting

** "FDA briefing docs for flu vaccine read favorably," says brokerage Jefferies, adding, "We find the FDA's tone/analyses in the briefing doc as balanced"

** Separately, co appoints new chief commercial officer and widens its president's role to oversee certain franchises, preparing for potential product launches over the next couple of years

** Including session's move, stock up 81.2% YTD