How do vaccines work?

Short Answer

Vaccines help children develop immunity against specific infectious diseases without suffering from the actual diseases. Vaccines contain the same antigens (a foreign substance that causes an immune response) or parts of antigens that cause diseases, but the antigens in vaccines are either killed or greatly weakened. Vaccine antigens are not strong enough to cause disease, but they are strong enough to make the immune system produce antibodies against them. Memory cells prevent re-infection when they encounter that disease again in the future.


Here’s a helpful video with more information:

Children are born with an immune system composed of cells, glands, organs, and fluids located throughout the body. The immune system recognizes germs that enter the body as “foreign” invaders, or antigens, and produces protein substances called antibodies to fight them. A normal, healthy immune system can produce millions of these antibodies to defend against thousands of attacks every day, doing it so naturally that people are not even aware it is happening. Antibodies often disappear once they have destroyed the invading antigens, but the cells involved in antibody production remain and become “memory cells.” Memory cells remember the original antigen and then defend against it if the same antigen attempts to reinfect a person, even after many decades. This protection is called immunity.

Disease prevention is key to public health. It is always better to prevent a disease than to treat it. Vaccines can protect both the people who receive them and those with whom they come in contact. Vaccines are responsible for the control of many infectious diseases that were once common in this country and around the world, including polio, measles, diphtheria, pertussis (whooping cough), rubella (German measles), mumps, tetanus, and Haemophilus influenzae type B (Hib). A successful vaccination program eradicated smallpox, one of the most devastating diseases in history. Over the years, vaccines have prevented countless cases of infectious diseases and saved literally millions of lives.

Vaccine-preventable diseases have a costly impact, resulting in doctor’s visits, hospitalizations, and premature deaths. Sick children can also cause parents to lose time from work.