Question: How do vaccines work?

Josh Meyers answered on 23 Jun 2015:

Vaccines work by introducing a small dose of inactivated virus into the body. The body then produces antigens to degrade the virus. These antigens are stored so that when the body sees the virus again (in its active form), it is already primed to degrade and destroy it.

There are many ways a virus can be inactivated. One way is by growing the virus in animal cells (such as baby chick embryos) until it loses the ability to replicate in human cells.