These are substances given to you to help protect your body from disease. Vaccines can be made from dead or weakened germs, or from portions of germs. A vaccine introduces your body to a disease in a safe way. It stimulates your body's immune system to protect you against the disease without causing you to become sick.

How They Are Given

There are many different types of vaccines. Some are injected. Some are given orally. Some are given as a nasal spray. Some vaccines are effective after one dose. Others require a series of doses. And some require booster doses later in life to maintain your body's defenses.

How They Work

When a vaccine enters your body, your immune system gets to work. It sees the germs of the vaccine as foreign invaders. Your white blood cells produce special proteins called "antibodies." They are custom-tailored to fight and destroy these specific germs. And your immune system remembers this process forever. If you come into contact with a disease you've been vaccinated against, your body can quickly attack and destroy the germs before they make you sick. This preparedness is called "immunity."

Protecting Public Health

Vaccines help prevent the spread of serious illnesses. Diseases that were once common (such as polio, mumps and tetanus) are now rare because of vaccines. A vaccination program wiped out smallpox, a serious and highly infectious disease.

Vaccine Safety

Vaccines are held to the highest standard of safety. All are tested and monitored to ensure that they do not cause health problems. If you choose not to be vaccinated, you put yourself and those around you at greater risk for disease.