Seniors were one of the main groups urged to get a flu shot this season but for many of them, the vaccine didn't work.
The CDC says the vaccine helped just 9 percent of people aged 65 and older.
For those under 65, the vaccine was about 56 percent effective.
Researchers say they're not sure why the vaccine didn't do much to help older people.
But the CDC says even with the disappointing numbers, it's still worth it for everyone to get a flu shot.