Which option best states the central idea of the passage about how vaccines work?

Read the passage: A vaccine works by training the immune system to recognise a disease-causing germ without the person having to suffer the illness itself. It usually contains a weakened or killed form of the germ, or just a harmless piece of it. The body responds by making antibodies and special memory cells. If the real germ later invades, these cells recognise it and mount a rapid defence before it can cause serious harm. The idea dates back to 1796, when the English doctor Edward Jenner showed that material from cowpox sores could protect people against the far deadlier smallpox. Nearly two centuries later, after a worldwide vaccination campaign, smallpox became the first human disease ever to be declared eradicated.

1. A Option A: Vaccines prepare the body to fight germs, an idea that has had enormous success.
2. B Option B: Cowpox is a more dangerous disease than smallpox.
3. C Option C: Memory cells are produced only after a person falls seriously ill.
4. D Option D: Edward Jenner was the only doctor of his time to study smallpox.

Answer checked 11 October 2026 · How we write and check questions