My friends. It is IMPOSSIBLE to get the flu from the flu shot. it is a dead virus incapable of causing illness. The mist is a different story, but still highly unlikely in anyone with a normal, uncompromised immune system.
People who get the shot can still get the flu, but it is generally less severe. Also, the vaccine generally only contains a few of the most popular strains, it does not encompass all strains and thus exposure to a strain that is not in the vaccine can make the person ill. Like most vaccines, it works best when MOST people are vaccinated thus reducing the spread in general.
Also, many, many times people diagnose themselves with the flu when what they have is a bad cold. Diff thing entirely that cannot be helped. Also, I have heard many people say they had the flu, when what they really had was a stomach virus, and not even flu symptoms.
And finally, it takes awhile for the flu shot to kick in and do its protecting. I hear so many people say "oh I got the shot and three days later I got sick!" thats prob because people get the flu shot when flu season has already started and were already exposed, or were exposed shortly after.
Flu shots are especially important for older adults. Several studies have shown that it can reduce the chances of cardiac events by as much as 50%..most likely because the illness can weaken and aggrevate heart conditions, so protection makes this damage less likely.