URL of this page: https://medlineplus.gov/vaccines.html


Also called: Immunization, Vaccination


What are vaccines?

Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. For example, there are vaccines to protect against

Most vaccines contain germs (or parts of germs) that cause disease. The germs have been killed or weakened enough that they won't make you sick. But they will spark an immune response, which helps your body fight off the germs. Your immune system will also remember the germ and attack it if that germ ever invades again. This protection against a certain disease is called immunity.

The COVID-19 vaccines that are authorized in the United States work differently. They are mRNA (messenger RNA) vaccines. mRNA vaccines teach your cells how to make a protein (or just a piece of a protein) that triggers an immune response. This builds immunity and protects you from getting infected if the real virus enters your body.

What are immunization and vaccination?

Immunization is the process of becoming protected against a disease. But it can also mean the same thing as vaccination, which is getting a vaccine to become protected against a disease.

Why are vaccines important?

Vaccines are important because they protect you against many diseases. Since these diseases can be very serious, it is safer to get immunity from a vaccine than from getting sick with the disease. And for a few vaccines, getting vaccinated can actually give you a better immune response than getting the disease would.

Vaccines not only protect you; they also protect the people around you. This idea is called community immunity or herd immunity.

Normally, germs can travel quickly through a community and make a lot of people sick. If enough people get sick, it can lead to an outbreak. But when enough people are vaccinated against a certain disease, it's harder for that disease to spread to others. This means that the entire community is less likely to get the disease.

Community immunity is especially important for the people who can't get certain vaccines. For example, they may not be able to get a vaccine because they have weakened immune systems. Others may be allergic to certain vaccine ingredients. And newborn babies are too young to get some vaccines. Community immunity can help to protect them all.

Are vaccines safe?

Vaccines are safe. They must go through extensive safety testing and evaluation before they are approved in the United States.

What is a vaccine schedule?

A vaccine, or immunization, schedule lists which vaccines are recommended for different groups of people. It includes who should get the vaccines, how many doses they need, and when they should get them. In the United States, the Centers for Disease Control and Prevention (CDC) publishes the vaccine schedule.

It's important for both children and adults to get their vaccines according to the schedule. This makes sure that you get protection from the diseases at exactly the right time.

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