I don't know all the in's and out's of it...but from what I understand, you cannot get the flu from a flu shot.
The flu shot vaccine is made from dead, inert virus.
Now, again, as I know it....that shot will help you past numerous flu strains, but not every one of them. Sort of immunization from all the clubs, hearts and spades of a deck of cards, but not the diamonds.
I suspect that if you already had a virus lurking when you got the shot, it appeared, that basicly is your bad luck.
I have heard of some reactions, most are minor. Aches and discomfort at the injection site, but others, I suspect were more a reaction to the medication, not really the flu.
Our hospital, along with most organizations, strongly suggest that nurses, docs and other health care workers get the flu shot. Also those in those groups such as the elderly, immuno-suppressed, etc.
Hope that helps.