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Scientists discover why seniors get limited benefit from flu shot

Seniors could benefit from a special flu vaccine that provides an added kick to their immune systems, a new study suggests.

Previous research has shown that older folks don't gain the same level of protection from the annual flu shot, compared to the rest of the population. For instance, the influenza vaccine protects 70 to 90 per cent of younger adults from infection. But vaccine efficacy ranges from just 17 to 51 per cent in those over 65.

Scientists weren't sure why the vaccine has limited benefit in this older group. Are seniors not capable of making effective antibodies to combat the bug? Or, don't they produce enough antibodies to ensure maximum protection?

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So U.S. researchers - led by Xiao-Song He at Stanford University School of Medicine and Patrick Wilson at the University of Chicago - conducted a complex series of laboratory tests to settle the issue.

Their findings, published this week in the Journal of Clinical Investigation, revealed that the problem stems from a decreased production of virus-targeting antibodies. In other words, "it's an issue of quantity, not quality," said Dr. Wilson.

"This was an important question to answer because the quality and quantity of antibodies are regulated by different biological pathways," said Dr. He. "Now that we know the reason, we can try to figure out how to fix the problem."

Vaccine manufacturers are already exploring new types of vaccines. Some shots contain a higher than usual dose of the vaccine. Others contain boosters known as adjuvants that provide additional stimulation to the immune system. Clinical trials will be needed to identify the best approach, said Dr. Wilson.

Meanwhile, in the journal Science, Swiss and British researchers report progress toward the ultimate goal of a universal flu vaccine that guards against most strains of the quickly evolving virus. If further work proves successful, it could eventually do away with the need for a new flu shot every year.

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