Every day our bodies are bombarded by bacteria and viruses. The ones that get inside our body meet our immune system which is ready not only to kill the invaders but also to create memory cells that will help defeat them more quickly the next time they try to attack.

When people are vaccinated against a disease, they are purposely given the bacteria or virus that causes the disease. They can receive the vaccine in a shot, by mouth, or by a nose spray.

Shots protect you by giving you only a tiny piece of a disease-causing germ or by giving you a version of the germ that is dead or very weak. (Giving a whole germ that’s alive would give you a disease (like measles or chickenpox).

But giving only this tiny, weakened, or dead part of the germ does not give you the disease. Instead, just the opposite happens. Your body responds to the vaccine by making antibodies. These antibodies are part of your immune system, and they can fight the disease if you ever come in contact with that nasty germ.

It causes little if any sickness in the person who receives it. Instead it causes the body’s immune system to make proteins called antibodies, which fight disease. If the same bacteria or virus enters the body later on, the immune system will know how to fight it off.

Vaccines are substances that prevent the spread of disease. Giving people vaccines can save millions of lives. For example, smallpox killed some 2 million people in 1967. By 1979 the disease had disappeared! This was because there was a worldwide program of vaccination.


An English doctor named Edward Jenner created the first vaccine in 1796. He saw that people who got the mild disease called cowpox rarely got smallpox, which is more serious. He did experiments to find out why.

He scratched material from a cowpox sore into the skin of a healthy boy. The boy got cowpox. Then Jenner scratched material from a smallpox sore into the boy’s arm. The boy stayed healthy. The cowpox material was a vaccine against smallpox. This was because the boy’s immune system learned from the cowpox which antibodies to make to protect the body from more cowpox as well as smallpox.

The French scientist Louis Pasteur was another important researcher. In the 1880s he developed a vaccine against rabies. He used a weakened form of the rabies virus to protect against a full attack by the same virus.

Since Pasteur’s time, scientists have produced vaccines against many diseases. In the middle of the 1900s Jonas Salk created a vaccine that almost wiped out polio. Polio can paralyze people so they can no longer walk and sometimes so they can’t breath.

Vaccines have also been developed for mumps, measles, cholera, plague, tuberculosis, influenza, and hepatitis.

When your body is protected from a disease in this way, it’s called being immune to an illness. In most cases, it means you won’t get the illness at all. But sometimes, you can still get a mild case of the illness.

This can happen with chickenpox. Even kids who get the shot to prevent chickenpox can still get a case of it. The good news is that they usually don’t get a very bad case of it. Milder cases mean fewer spots and less itching.

First Shots

The good news is that kids get a lot of the shots they need by age 2. So if you’re old enough to read this article, you’ve already had most of your shots! After that, a kid doesn’t need many more unless a new disease comes along. Like COVID-19.

Kids get a few shots when they’re between 4 and 6 years old. The next set of shots isn’t usually until kids are about 11 or 12 years old.

Most kids should get the flu vaccine each year. Now, instead of a shot, many kids can get it as a nasal spray. This is a mist that is sprayed into the nostrils, so there’s no needle. The shot and the nasal spray work equally well. Your doctor will suggest which is best for you.

Why do we need vaccines?
Shots are great for individual kids because it means that they won’t get those serious diseases. But shots are great for the health of the country and world too. How? When almost all kids have had these shots, it means that these illnesses don’t have much of a chance to make anyone sick.

Because most kids in the United States get all their shots, you rarely meet anyone who has had diseases like measles or mumps. Your mom or dad has probably had to show your school that you’ve had all your shots. Schools and camps do this because they don’t want the kids spreading or catching serious illnesses.

It’s OK if you don’t like shots. But remember that they are the best way to protect yourself and others.


Britannica Kids



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