Health officials say this season's flu shot is only 9 percent effective in protecting seniors against the most common and dangerous flu bug.
Flu vaccine tends to protect younger people better than older ones and is never 100 percent effective. But experts say the preliminary results released Thursday are disappointing and highlight the need for a better vaccine.
For all age groups, the vaccine's effectiveness was a moderate 56 percent.
But it did a particularly poor job of protecting those 65 and older against a harsh flu strain that is causing most of the illnesses this year. Health officials emphasize that some protection though is better than none at all.
The flu season started early this year but the worst of it is over.
Explore further: Flu season off to latest start in decades