Flu shot not even 50% effectiveFebruary 21, 2013
This year's flu vaccine provided little protection to people 65 and older who got a shot, new data released by the U.S. Centers for Disease Control reveal.
The study estimates how well the vaccine did at preventing people from becoming sick enough to need to see a doctor, preventing "medically attended flu" in influenza science parlance. And the data suggest this year the vaccine didn't perform very well for older adults.
It found that a flu shot cut an older adult's risk of contracting a case of influenza A H3N2 that needed medical care by only nine per cent.
When the scientists calculated the overall effectiveness, the vaccine's ability to prevent medically attended flu caused by both flu A and B viruses, the estimate was 27 per cent for older adults.
The findings are disappointing given the H3N2 component in this year's vaccine is well matched to the viruses circulating. Paradoxically, the B component of the vaccine isn't as closely matched to circulating viruses, yet it is performing better, according to the study.