To understand how vaccines work, it helps to first look at the immune system.
The immune system is a network of cells, tissues and organs that work together to protect you against disease.
When disease-causing germs such as viruses or bacteria enter your body, the immune system responds by making proteins called antibodies. These antibodies work with the rest of the immune system to destroy the germs.
The first time your body is exposed to a germ, it takes time for the immune system to respond and make antibodies. In the meantime, you could become sick. But after the first exposure, the immune system usually remembers the germ and how to fight it. Then, if you are exposed to the germ again, your immune system quickly responds to destroy the germ before it makes you sick.
Vaccines teach the immune system how to recognize and fight off specific disease-causing germs. They help protect you against disease without the risk of getting sick first.
Vaccines contain killed, weakened or manufactured versions of the disease-causing germ or parts of the germ called antigens. Some vaccines contain instructions that your body’s cells use to make the antigen rather than the antigen itself.
When you get a vaccine, your immune system responds to the antigen as if it were exposed to the germ. It makes antibodies and remembers how to destroy the germ. Then, if you get exposed to the germ, your immune system can recognize it right away and quickly fight it off.
While most vaccines are highly effective at preventing disease, no vaccine is 100 percent effective. Not everyone will get fully protected after immunization. But those who get a disease despite being immunized are less likely to become seriously ill.
It's much safer to get a vaccine than to get the disease it prevents.
When you get immunized, you’re not just protecting yourself, you’re also helping protect your entire community. The more people in a community who are immune to a disease, the harder it is for a disease-causing germ to spread and the entire community is better protected. This is called community immunity (or herd immunity).
Community immunity helps protect everyone, but it is especially important for protecting people who cannot get immunized, such as very young babies and people with certain medical conditions. Community immunity is also important for people who may not be fully protected by immunization, such as those with weakened immune systems.
Vaccines aren't 100 percent effective, and community immunity does not provide full protection to those who cannot be protected by vaccines. But these people will be less likely to get sick, thanks to those around them being immunized.
Community immunity is another important reason for you and your family to get all recommended vaccines.
Learn about the science behind vaccines and how they work.
A look at how vaccines and group immunity can protect you, your family and your community.
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