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How Do Vaccines Help Your Body Fight Diseases?
疫苗是如何帮助身体抵抗疾病的？
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Vaccines contain weakened or inactive parts of a virus or bacteria.
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When injected, they safely train your immune system to recognize real threats.
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White blood cells learn to make special proteins called antibodies against the invader.
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If the real disease enters your body later, your immune system responds much faster.
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This rapid response often stops illness before symptoms even begin.
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Some vaccines require multiple doses to build strong, lasting protection.
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Herd immunity occurs when enough people are vaccinated to block disease spread.
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Vaccines have helped eliminate deadly illnesses like smallpox worldwide.
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Scientists continuously update flu vaccines because flu viruses change every year.
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Side effects are usually mild, such as soreness or a low fever for one or two days.