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How Vaccines Work

How Vaccines Work

Vaccines help you develop immunity (protection from disease) by imitating an infection and triggering an immune response. But unlike the real infection, vaccines do not cause illness.


Vaccines are made using either a weakened or killed version of the pathogen (virus or bacteria) that causes the disease, or parts of the pathogen (antigens). Once in your body, the vaccine triggers your adaptive immune system to respond (in the same way it would to the actual pathogen), producing antibodies and training your body to recognize and fight off the pathogen. That way, if you are ever exposed to the actual pathogen in the future, your immune system is able to quickly recognize it and destroy it before it makes you sick. This is how you get immunity from vaccines.

Vaccines don’t just protect the person getting vaccinated, they protect everyone around them too. When most people in a community are vaccinated, it makes it harder for disease to spread. This indirectly protects those who can’t get vaccinated, such as babies who are too young to be fully vaccinated and people who can’t get certain vaccines for medical reasons. This type of protection created when most people are vaccinated is called herd immunity.

Watch the video and then review the Immunity Warriors: Invasion of the Alien Zombies comic to learn more about how vaccines work.






See More Sample Lessons

Each lesson is accompanied by a quiz that lets students earn vaccines for UNICEF based on their score! Register to unlock all lessons and quizzes for free:


Last modified: 
Feb 27, 2018