How vaccines work

You may already understand just how important vaccines are to help keep you, your family, and your community safe. Vaccines are one of the strongest tools of preventative medicine that we have to protect against disease and illness – but you may not know exactly how they work.  We’re here to walk you through the details. 

When someone gets sick, their body is often able to build up an immunity to the disease they’ve encountered — but they have to first fight off the disease and recover. An invading germ — like a virus or bacteria — enters and attacks the body, multiplies, and causes illness. In response, the body’s immune system springs into action. White blood cells, also called immune cells, help fight the infection, in part by producing proteins, called antibodies. Antibodies identify the invading germs, enabling the white blood cells to attack them and fight off infection. Many antibodies are precise, responding to only specific types of germs. For example, antibodies that fight the flu are not the same as those that fight chickenpox.

In this way, the immune system is a carefully orchestrated powerhouse built to  fight off invading germs. And once a person has produced antibodies to a particular virus or bacteria, they’ve developed an immunity to that particular disease. However, sometimes the response is too late to prevent serious illness or complications. 

This is where vaccines come in — they help a person build immunity to disease without having to get very sick first. Vaccines are built from dead or weakened forms of a virus or bacteria, a piece of virus or bacteria, or a byproduct made by bacteria. When a person’s body encounters the vaccine, it produces antibodies, thinking it is responding to a real threat. So the flu vaccine helps the body produce flu antibodies, and the chickenpox vaccines helps the body produce chickenpox antibodies. Those antibodies stay in the body until they are needed, like when the body encounters the actual virus or bacteria. If you encounter flu germs after you’ve had your flu shot, you’re unlikely to get sick. If you do, you’ll likely only experience mild symptoms.  

You might have noticed that your child’s vaccine schedule in the first year — and then on through childhood — contains some vaccines that only need to be administered once, and others that require multiple doses or a “booster” shot.  The flu vaccine, for example, needs to be given annually because the influenza virus can change so much from year to year, so the vaccine needs to be regularly updated. It’s also worth noting that while some newborn babies are immune to certain diseases because of antibodies received from their mothers, that immunity doesn’t last very long, so it’s important to follow a recommended vaccine schedule to protect  Baby from disease.

As always, if you have any questions about how vaccines work or your child’s immunization schedule, make sure to speak with your child’s healthcare provider for more guidance. 

Learn more about vaccines

  • “How Do Vaccines Work?” The American Academy of Pediatrics, February 26 2019. Retrieved March 23 2020.
  • “Understanding How Vaccines Work.” Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, July 2018. Retrieved March 23 2020.

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