NEW YORK ( MainStreet) -- Researchers at the University of Minnesota are calling for stronger seasonal flu shots after discovering the yearly vaccination prevents only about 59% of seasonal flu infections in adults.

Some shots were more effective than others. H1N1 (swine flu) shots were found to be 69% effective for adults under 65, as were flu vaccines delivered as nasal spray to children between 6 months and 7 years old, which were found to be 83% effective.

Seasonal flu shots have come under fire after a study found that the vaccine prevents only about 59% of infections in adults.

The

results

are based on an analysis of 5,707 vaccination studies conducted during the past 44 years. Researchers say there is no adequate data that speaks to the flu vaccine's effectiveness on older Americans.

Researchers recommend that Americans get the current vaccination despite the inherent limitations, but they also urge world health officials to develop more effective ones.

"The ongoing public health burden caused by seasonal influenza and the potential global impact of a severe pandemic really signals the urgent need for a new generation of highly effective and cross-protective vaccines that we can produce rapidly," lead author Michael Osterholm said in a

written statement

.

The U.S. Centers for Disease Control and Prevention

recommends that anyone 6 months or older get an annual flu shot

.

Want more information on flu shots? Check out our

health hot topic.

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