The Food and Drug Administration has approved a new influenza vaccine for older adults manufactured by Moderna. The vaccine is authorized for adults 50 to 64, but the FDA also granted an accelerated approval for adults 65 and over. Scientists have suggested mRNA technology will lead to more effective flu shots, because it allows vaccine makers to more quickly respond to changes in flu strains. The Moderna vaccine uses messenger RNA — a synthesized genetic code that carries instructions on how to make flu virus proteins. Tens of thousands of flu deaths are reported in the United States in most years, and they primarily occur among older adults and people with weakened immune systems.