JAMA : the journal of the American Medical Association
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Despite strong worldwide guideline recommendations, influenza vaccination rates remain suboptimal among young and middle-aged patients with chronic diseases. Effective scalable strategies to increase vaccination are needed. ⋯ In a nationwide randomized clinical implementation trial, electronically delivered letter-based nudges markedly increased influenza vaccination compared with usual care among young and middle-aged patients with chronic diseases. The results of this study suggest that simple, scalable, and cost-efficient electronic letter strategies may have substantial public health implications.