What is a vaccine, and how does vaccination protect against a disease?

A vaccine is a preparation of killed, weakened or fragmented pathogens, or of their toxoids, that is introduced into the body. It provokes the immune system to make antibodies and, more importantly, memory cells, without causing the disease. If the real pathogen enters later, the memory cells produce antibodies quickly and in quantity, so the disease does not develop.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

This is active acquired immunity and it usually lasts for years.