What's up Doc: What are vaccines Published July 19, 2007 By Capt. (Dr.) Derrick Storey 47th Medical Group LAUGHLIN AFB, Texas -- There are so many shots called "vaccines." What is a vaccine? Your immune system, which defends your body against infection, works by recognizing something in your body as foreign verses your own. Your immune system also fights off an infection faster and better if it recognizes it from a previous exposure; sometimes, it fights off the infection so fast that you don't even notice getting sick. A vaccine is either broken up parts of an infectious agent or a live (but very, very weak) form introduced into the body to teach your immune system to recognize it as foreign. This is particularly important against viruses, which there are very few medications to directly treat. There is also something population biologists call "herd immunity." Despite the fact that none of us particularly like being considered a herd, it holds a singular idea. By immunizing enough people, even those not immunized are protected because they simply don't come into contact with the bug or the vaccine is spread from the vaccinated person to others by simply breathing such as the oral Polio and the nasal form of Influenza vaccine. So, you have to treat as many people as possible in hopes of getting to that high-mark. If you would like to learn more about why we immunize, I recommend the following website: www.cdc.gov/nip/publications/fs/gen/why.htm.