十万个为什么·科学启蒙30篇（1）

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疫苗如何训练我们的免疫系统？

Vaccines introduce harmless versions of germs—or just key parts of them—so your body can practice fighting without getting sick.
Your immune system responds by producing specialized white blood cells called B cells and T cells that recognize the invader’s unique markers.
Some of those cells become ‘memory cells,’ which remain in your body for years or even decades after vaccination.
If the real pathogen later enters your body, memory cells activate much faster and stronger than during the first encounter.
This rapid response usually stops infection before symptoms develop—or makes illness far milder and shorter.
mRNA vaccines, like those used for COVID-19, deliver genetic instructions so your own cells temporarily make a harmless viral protein.
Your immune system then learns to target that protein, just as it would during a real infection.
Booster shots refresh memory cell numbers and improve protection, especially as immunity naturally fades over time.
Vaccines don’t overload your immune system—your body deals with thousands of foreign molecules every day from food and air.
Herd immunity emerges when enough people are protected, making it harder for diseases to spread and shielding those who can’t be vaccinated.