The Center for Disease Control announced the flu vaccine was 29 percent effective this season.
Experts say it's because it wasn't a match to fight a flu strain that started making the rounds mid-season.
The vaccine is typically about 40 percent effective.
In the 2014-2015 season the shot was just 19 percent effective.
Officials are already starting to formulate next year's shot.
For more information about the vaccine or CDC, click here.
