How does vaccination protect a person from a disease?

How does vaccination work

Vaccination protects a person from disease because of

Which of the following method of contraception protects a person from acquiring a sexually transmitted disease ?

BCG vaccine provides protection from:

Small pox diseases has been erradicated from out conuntry. We are very close to erradicate one more disease from our conuntry for which government has launched door to door programme for providing vaccination. Name such disease. List atleast three other vaccines which are given to newly born babies to protect them from many diseases.