十万个为什么·科学启蒙30篇（4）

9 / 30

为什么疫苗能帮助预防疾病

Vaccines introduce harmless versions of pathogens—such as weakened viruses, protein fragments, or mRNA blueprints.
These trigger dendritic cells to present antigens to T and B lymphocytes, launching a targeted immune response.
Memory B cells remain ready to produce antibodies within hours if the real pathogen invades later.
Memory T cells recognize and destroy infected cells faster, stopping disease before symptoms appear.
Multiple doses boost immunity by encouraging stronger, longer-lasting memory cell production.
Herd immunity emerges when enough people are vaccinated, reducing transmission and protecting those who cannot be.
Side effects like sore arms or mild fever show the immune system is actively learning—not that the vaccine caused illness.
mRNA vaccines don’t alter DNA; they simply instruct cells to make one safe viral protein for recognition.