Vaccines

A vaccine shows the immune system a harmless version of a germ - killed or weakened, a piece of it, or instructions for the body's cells to make that piece - so it learns to recognise the germ without the illness. When enough people are immune, a germ can't spread (community immunity), which protects those who can't be vaccinated.

Watch · Depth 1 · 82 sPractice without the illnessA vaccine lets your immune system learn a germ without getting ill. How that works, how it protects people who can't be vaccinated, and what vaccines have done, from smallpox to measles.