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MALTA—Efforts to create a universal flu vaccine, one that would do away with the annual reformulations, is a hot topic these days in the infectious disease community. But in the bigger picture of reducing flu transmission—and reducing the thousands of deaths it causes in the U.S. each year—there is a big leap forward that could be taken with already available tools. Researchers and public health officials these days agree that a vast improvement now would simply involve inducing more people to get existing annual flu shots.