Chapter 10 — Science & Nature
How do vaccines work?
A vaccine shows the immune system a harmless piece or weakened form of a pathogen so it can build antibodies and memory cells in advance. If the real pathogen arrives later, the response is faster and stronger than a first infection.
Follow-up questions
What's the difference between mRNA and traditional vaccines?
mRNA vaccines deliver instructions for cells to make one viral protein; traditional vaccines deliver the protein, an inactivated virus, or a weakened live virus directly.
Why do some vaccines need boosters?
Antibody levels naturally fall over time and some pathogens mutate. Boosters re-expand the memory cell population and update the target.
What is herd immunity?
When enough of a population is immune that chains of transmission break, protecting those who can't be vaccinated. The threshold varies by disease — measles needs about 95%.
Why do vaccines cause side effects?
Sore arm, fatigue, and mild fever are the immune response itself, not the pathogen. They usually resolve within 48 hours.
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