"Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America's seniors. Company research involving more than 40,000 people found that mFLUSIVA is safe and appears to produce stronger protection than traditional flu vaccines. The FDA initially refused to even consider reviewing Moderna's mRNA flu shot. Many public health officials say the mRNA flu vaccine has other advantages as well. That could make the vaccine more useful when a new flu strain emerges unexpectedly, which occurred last flu season.