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What are Vaccines and How Do They Work?


Between 1949 and 1954 over 11,000 Canadians were paralyzed by a disease called polio and many died. A disease is different from an infection. As you’ve learned, an infection happens when germs enter your body and begin to grow. Disease happens when parts of your body are damaged as a result of the infection. When a person begins to get signs and symptoms of an illness like polio, the germ or virus that causes polio has gotten past all the bodies defenses and has caused disease. Thankfully we don’t have to worry about polio here in Canada anymore. That’s because scientists were able to use their understanding of how the immune system works to find a way to protect people from diseases like polio through vaccines. Let’s examine what vaccines are and how they work. 

patient in an iron lung

What are vaccines?

Vaccines are substances that give you immunity to disease. Remember, “immunity” means you are protected against something. Unlike most medicines that treat or cure diseases, vaccines prevent them in the first place. Vaccines play a very important role in keeping us healthy. They protect us against diseases that can be very serious and even deadly. Examples are measles, meningitis and polio. Most vaccines are given by a needle but some are given orally (by mouth). Vaccines are also called vaccinations, immunizations, shots and needles. You might remember getting vaccines when you were younger. Vaccines are also given in school.

How do vaccines work?

Vaccines are made using either weakened or dead versions of the germs, or parts of the germs that they are made to protect against. But unlike the real germs, the germs used in vaccines do not make you sick. That’s because they are either weakened or dead. When you get a vaccine, your body is tricked into thinking it is infected with the actual germ. This causes your immune system to respond in the same way it would to a real infection. Your body calls on your specialized white blood cells to make antibodies. And just like after a real infection, your immune system remembers the germ. It now knows how to fight that germ. That way, if the actual germ invades your body in the future, your immune system knows what it needs to do to fight it off before it can make you sick. This is how you get immunity from vaccines.

But all of that doesn't happen instantly! Your body takes about two weeks after getting vaccinated to gain immunity from a vaccine.

Herd Immunity

When you get vaccinated, you’re not just protecting yourself. You’re protecting your friends, family and others in your community too. That’s because if you don’t get the disease in the first place, you can’t spread it to others.

The more people in a community who are vaccinated, the harder it is for a disease to spread. That’s because if a person infected with disease comes in contact only with people who are immune (have been vaccinated), the disease will have little opportunity to spread. This helps protect everyone, including babies who are too young to be fully vaccinated and those who can’t get certain vaccines for medical reasons, such as a child receiving treatment for cancer. This type of protection created when most people are vaccinated is called herd immunity.

How well do vaccines work?

Vaccines work really well. They prevent diseases that can make us really sick. Before vaccines were available, many Canadians died or were hospitalized from diseases such as measles, diphtheria and polio that we can now prevent with vaccines. Thanks to vaccines we rarely see diseases like these in Canada anymore.

This infographic from the Public Health Agency of Canada compares the number of cases of six different diseases in Canada before and after the introduction of each vaccine. It shows just how well vaccines work!

Disease Cases THEN Cases NOW Decrease
Whooping Cough 17,777 2,332 87%
Measles 53,584 292 99%
Mumps 36,101 103 99%
Rubella 14,974 1 99%
Diphtheria 8,142 1 99%
Polio 2,545 0 100%


Take a look at the infographic above. What diseases are no longer making Canadians sick? You may be surprised to know that Canada was declared polio-free in 1994. Health organizations across the world are working to provide polio vaccines to all children. Some experts believe that the poliovirus could be removed or eradicated from Earth in the next couple of years. Your correct answers in the quizzes that provide vaccines for kids in need are part of the global effort to improve the health of all children.

Fun fact: Vaccines save 2-3 million lives worldwide every year! (Source - WHO)

All lessons & quizzes are free!

 This was just one of the lessons in our Immune System and Vaccines section. There are over 60 lessons on Kids Boost Immunity just like this one on a variety of subjects. Each lesson includes a quiz, and every time a student scores 80% or higher on a quiz, we will donate life-saving vaccines to UNICEF Canada. Sign up now!

To see other sample lessons, click here.

  Oct 28, 2019