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 the Centers for Disease Control and Prevention said Thursday.
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.
Thirty San Diego County residents died from influenza this flu season according to the County Health and Human Services Agency.
The number of recent deaths exceeded the county's previous record of 22 flu-related deaths in the 2003-04 season, not including the H1N1-related deaths from 2009 through 2011.
While it's likely that older people who were vaccinated are still getting sick, many of them may be getting less severe symptoms.
"Year in and year out, the vaccine is the best protection we have," said CDC flu expert Dr. Joseph Bresee.