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The Power of Memory: Fighting Disease With Vaccines & Immunization

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  • Immunization helps the body’s immune system develop protection against some infectious diseases. Discover how vaccines produce immunity to a disease by helping the immune system learn to recognize and fight the germ that causes the disease. Explore the links to MedlinePlus health topic pages and for trusted information about immunization and vaccine research.

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    • The Power of Memory: Fighting Disease With Vaccines & Immunization

      Immunization & Vaccination

      Immunization is an important process that helps keep people healthy. It protects individuals and communities from diseases that can be serious and sometimes, even deadly. Through the immunization process, you become immune to, or protected from, a disease. Immunization begins when you receive a dose of a vaccine, which is usually given with a shot. This is known as a vaccination. Before vaccines were available, people could only become immune to certain diseases by catching and recovering from the actual disease, which was risky since people could get very ill or die.

      Vaccines have had an enormously positive impact by preventing disease around the globe. Vaccination is the most effective method of protecting people from infectious diseases such as influenza, tetanus, human papillomavirus, and many others. In addition, vaccines have completely eradicated smallpox and have greatly reduced polio in the world.

      Your Immune System & Immunization

      Your immune system is a complex network of organs, tissues, cells, and chemical signals that work together to detect and fight disease-causing germs. While your immune system regularly fights germs on its own, it cannot effectively fight every germ your body encounters. So, vaccines are used to mimic an infection during the immunization process and help your immune system learn to recognize specific germs so it can keep you from getting sick.

      How Vaccines Work

      Vaccines are made from very small amounts of weak germs, dead germs, parts of germs, or toxins from germs that can cause disease…because only the actual germ or its parts can effectively train your immune system. The parts of the disease-causing germs found in the vaccine that stimulate your immune system are called antigens.

      When your health care provider gives you a vaccine, it triggers a complex cascade of events in your immune system. First, a type of immune cell called an antigen-presenting cell finds and engulfs the antigen in the vaccine. The antigen-presenting cell displays the antigen on its surface as a signal for other immune cells to detect. These other immune cells, known as T-lymphocytes or T cells, recognize the antigen and become activated and multiply. At the same time, T cells alert other immune cells known as B-lymphocytes or B cells to the presence of the infection. The B cells then start producing proteins called antibodies. Antibodies recognize and bind to antigens on germs and on infected cells, marking them so that T cells can then find and destroy them. Once these steps in the immunization process are over, some of the T and B cells that were activated go into hibernation as “memory” cells. Therefore, your immune system remembers the infectious germ…and if the same germ infects you later, the memory cells spring into action, quickly produce antibodies, and destroy the germs before you get sick.

      Community Immunity

      Vaccinating individuals can help keep your whole community healthy. When enough people are vaccinated and become immune to a germ, it is harder for the germ to spread from person to person – so only a few, if any people get infected. This is known as “community immunity” or “herd immunity.” While community immunity protects everyone, it is especially important for protecting people who aren’t eligible for certain vaccines, such as infants, elderly people, and people with weakened immune systems.

      Vaccine Safety

      Every vaccine goes through extensive quality and safety testing, including multiple clinical trials, where vaccines are tested on healthy people, and vaccines continue to be closely monitored after they are in use. These rigorous scientific procedures ensure that vaccines are safe and effective at training your immune system to protect you from a wide range of serious, infectious diseases.

      The National Library of Medicine offers trusted resources to educate you about immunization and how vaccines can protect you, your family, and your community. Start with and find Trusted Health Information for You!

      This video was produced by the National Library of Medicine

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Last Reviewed: May 7, 2021