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Cartoon illustrations of microbes

microbe is anything too small to be visible to the naked eye. Two types of microbes are bacteria and viruses. You’re surrounded by microbes all the time, and normally co-exist peacefully. Some types help you, like the bacteria in your digestive tract that help break down food. There are, however, some types of bacterium and viruses that can make you ill.

Bacteria are single-celled organisms. There are thousands of types of bacteria, and they live virtually anywhere. Bacteria are much bigger than viruses. (But they’re all way too small for you to see.) Bacteria are much more complex than viruses. Bacteria have the tools to reproduce themselves, by themselves. They are filled with fluid, and may have threadlike structures to move themselves, like a tail.

Virus. A virus may have a spiny outside layer, called the envelope. Viruses cannot reproduce on their own. They infect cells and take over their reproductive machinery to reproduce.



A vaccine essentially helps your immune system crack the code of a certain illness. A vaccine is usually made of the same cells that could make you sick, but they are weak or inactive. Sometimes a vaccine is made of cells that are very close, but not exactly the same, to the cells that would make you sick.

When a vaccine enters the body, the immune system responds the same way it would to any germ. The vaccine is easier to fight than the illness you’re being vaccinated against, and it won’t make you sick while your immune system fights it. Once the immune system figures out how to fight and defeat the antigens, it remembers what works against them. Should such an enemy enter your body again, your body will move to attack it before it has a chance to implement its plans to make you sick. Sometimes, your immune system needs a refresher course, which is why you get booster doses of some vaccines. Some antigens are especially tricky, and change over time, like flu viruses. That’s why people need to get flu shots every year to make sure they’re ready to take on the latest version.

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