This year, the wrong strain of flu was chosen for the vaccine. This happens every once in a while.
The flu vaccine cannot get you sick. It's not always effective (say, if the wrong strain is chosen), but getting the vaccine, even if it was the wrong strain, will still make symptoms less severe if the flu is caught. More often than not, people believe they have the flu after receiving a flu shot when they actually have a cold. Many people also wait until it's far to late into flu season for a vaccine to be effective. It takes at least two weeks after the vaccine is received for the immunity's efficacy. Getting a flu shot in the dead of flu season is taking a shot in the dark.