Because flu viruses mutate so fast, the only way to stop them is to destroy their ability to evolve. That's the key to creating a universal flu vaccine... and now we may have found the secret to creating one, and wiping out the flu.
The thing about the flu is that there's a lot of different strains. One flu season is different from the other and each one requires a new shot. That could change! Doctors believe we'll develop a universal vaccine soon enough.