How Do Vaccines Work?
When a person gets an infection, his or her body immediately goes to work making antibodies and preparing other defenses. But while the body is working hard to strengthen itself, the infection can grow, causing serious illness and even death.
Immunization exposes the body to a potentially infecting virus or bacterium that has been weakened or killed and made into a vaccine. This exposure allows the body to prepare to fight a specific infection before ever encountering the real infection, thus giving the body the time it needs to prepare (without the danger of the actual infection causing any serious harm). This head start greatly improves the body's ability to protect itself against the real infection. Today most vaccines stimulate immunity in more than 90 percent of recipients when properly administered.
Over the past several years, immunization levels have risen, indicating that our children have greater protection from common infections than ever before. However, these infections are still frequent in many other areas of the world. Failure to maintain high immunization levels would quickly put our children at risk of serious infection from bacteria or viruses brought into the United States from others parts of the world.