What is vaccination?
The best way to do this is to expose your body to killed or weakened viruses or bacteria (or parts of them), that can’t cause infection.
Unlike the early attempts at preventing disease, modern vaccines deliver only tiny amounts of inactivated or weakened viruses or bacteria, or parts of them. This allows your immune system to recognise the organism without you actually experiencing the disease.
Some vaccines need to be given more than once (i.e. a ‘booster’ vaccination) to make sure the immune system can overcome a real infection in the future.