Science
How does a vaccine work?
A vaccine works by safely teaching your immune system to recognize a germ before you ever encounter the real one. It shows your body a harmless piece or weakened version of the germ, so your defenses learn to fight it fast if it ever appears.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a vaccine works.
Step by step
- 1It exposes the immune system to a harmless form or piece of a germ.
- 2The body builds defenses, including antibodies and memory cells.
- 3If the real germ appears later, the immune system responds fast.
- 4This prevents illness or makes it much milder.
- 5Widespread vaccination also protects others through herd immunity.
Frequently asked questions
- How does a vaccine make you immune?
- It trains your immune system on a harmless version of a germ, so it remembers how to destroy the real one quickly before it makes you sick.
- Can a vaccine give you the disease?
- Standard vaccines use weakened, killed, or partial germs that can't cause the disease; at most you may feel mild, short-lived effects as immunity builds.
- How do mRNA vaccines work?
- They deliver instructions telling your cells to make a harmless piece of the germ, which your immune system then learns to recognize and attack.