Wow. A lot people in here buying into snake oil like colloidal silver.
Fact: You cannot get the flu from the shot. Once you get the shot it can take a couple weeks for it to do it's thing. If you get the flu after the shot, then that means you were exposed to a different strain, you were exposed before the shot took effect, or you already had the flu in your system before the shot.
Now it's entirely possible that you could have an allergy that would prevent you from getting the flu. In that case, god speed. A lot of people have mentioned things to 'prevent' the flu. That stuff is literally all bunk. The flu is a virus and the stuff mentioned has absolutely zero anti-viral properties.
This stuff is all fact. End of story