When people get the flu shot, they are getting a vaccine tailored to what strains the CDC thinks will be active this year - they are usually pretty accurate (I get the shot every September), but since the CDC is guessing six months ahead, they are not guaranteed.
This could be really cool - from the Beeb:
Universal flu vaccine comes closer, scientists say
Researchers say they are closer to developing a vaccine to give life-long protection against any type of flu, after promising trials in animals.
Two separate US teams have found success with an approach that homes in on a stable part of the flu virus.
That should remove the problem with current flu vaccines which must be given anew each year because they focus on the mutating part of the virus.
The proof-of-concept work is published in Science journal and Nature Medicine.
More faster please!