Concerns about flu vaccine

February 11, 2008 2:47:05 PM PST
There are concerns about this year's flu vaccine. Health officials say it may not be protecting Americans as well as expected.

The US Centers for Disease Control and prevention says slightly more than half of the influenza virus strains reported to its surveillance system are not good matches against the strains included in this flu season's vaccine.

The number of states reporting widespread flu activity jumped to 31 this week compared with 11 just one week ago. But the CDC says it knows from past influenza studies that the vaccine can still protect enough to make illness milder or prevent flu related complications.