Vaccines work by helping people safely imitate natural infections. That means that vaccines help protect you from diseases without ever having to risk the serious, and sometimes deadly, consequences of getting sick from those diseases.
When viruses or bacteria (germs) invade your body, they attack and multiply. This invasion is called an infection, and the infection is what causes illness. The first time your body encounters a germ, it can take several days for your body to make and use all the tools it needs to fight the infection. After the infection is over, your body’s immune system keeps a few “memory cells” that remember what it learned about how to protect against that disease, and if your body encounters the same virus or bacteria again, it will produce antibodies to attack the germ and protect you from the disease.
Vaccines help people develop immunity (protection) to a disease by safely imitating a natural infection. Some people may believe that natural immunity (which occurs after a person is infected by a bacteria or virus) is better than the immunity developed from vaccines. However, natural infections are dangerous because they can cause severe illness and lead to serious complications and even death.
Vaccines are made up of viruses or bacteria that are altered or weakened so that they only cause an imitation of the disease and not the disease itself. There are a variety of different ways to alter or weaken the viruses or bacteria in vaccines so they cause immunity instead of serious disease. Click below to learn more about the different types of vaccines. They include live attenuated vaccines, toxoid vaccines, inactivated vaccines, subunit vaccines and conjugate vaccines.
To see an example of how vaccines work, read the story of Chip and Dale from the Vaccine Education Center at Children’s Hospital of Philadelphia (CHOP).
You can also view CDC’s animated video that helps explain how vaccines help babies fight infections.