What is vaccination?
Vaccination protects children against serious diseases by stimulating the immune system against disease germs.
How does vaccine immunity differ from natural immunity?
Normally in most diseases the disease-germ enters the body, produces the disease & the body mounts fighting power against the germ and lastly one recovers from the disease. Here immunity against disease is produced after one has suffered from the disease.
A vaccine is nothing but whole or part of the disease germ, which has been processed or modified in such a way that it loses its capacity to produce disease but it can still induce fighting power in the body when administered. Hence by vaccination one develops immunity without suffering from the disease.
Rather than reinvent the wheel, I have decided to post a list of excellent detailed FAQs that interested parents can go to and read.
I would recommend the following links
3. Medicine Net http://www.medicinenet.com/vaccination_faqs/article.htm