The natural defense system of the human body
A short, two minute clip that explains how the immune system is activated by a vaccine:
"Our bodies are bombarded by bacteria and viruses. For those that make their way inside, our immune system is on guard, waiting not only to kill the invaders but also to create memory cells that will help defeat them more quickly the next time they try to attack. Vaccines, which are weakened versions of a disease like polio or measles, rely on the memory of our immune system to combat the real danger if it eventually enters our bodies."
History of Vaccination [clip]
Autism-Vaccine fears [LINK]
Making vaccines - interactive webpage