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Publications > Fact Sheets > General
How Vaccines Prevent Disease
Previously titled "How Do Vaccines Work?"

At a glance: Parents are constantly concerned about the health and safety of their children and they take many steps to protect them. These preventive measures range from child-proof door latches to child safety seats. In the same respect, vaccines work to safeguard children from illnesses and death caused by infectious diseases. Vaccines protect children by helping prepare their bodies to fight often serious, and potentially, deadly diseases.

Most vaccine-preventable diseases are caused by germs that are called “viruses” or “bacteria.” Vaccines to help prevent these diseases generally contain weakened or killed viruses or bacteria specific to the disease. Vaccines help your body recognize and fight these germs and protect you each time you come in contact with someone who is sick with any of these diseases.

There are a series of steps that your body goes through in fighting these diseases:

First A vaccine is given by a shot (influenza vaccine may be given by a nasal spray).
Next Over the next few weeks the body makes antibodies and memory cells against the weakened or dead germs in the vaccine.
Then The antibodies can fight the real disease germs if the person is exposed to the germs and they invade the body. The antibodies will help destroy the germs and the person will not become ill.
Finally Antibodies and memory cells stay on guard in the body for years after the vaccination to safeguard it from the real disease germs.

Most vaccines are given to babies and young children, but some are needed throughout your lifetime to make sure you stay protected. This protection is called immunity. Vaccines are an important and safe way to keep you healthy.

Why are vaccines important?
Most newborn babies are immune to many diseases because they have antibodies passed from their mothers. However, this immunity only lasts a year or less. Further, most young children do not have maternal immunity from whooping cough, polio, hepatitis B, or Haemophilus influenzae type b.

Immunizing individual children also helps to protect the health of our community. People who cannot be vaccinated will be less likely to be exposed to disease germs that can be passed around by unvaccinated children. Immunization also prevents disease outbreaks.

If your child is not vaccinated and is exposed to a disease germ, the child’s body may not be strong enough to fight the disease. Before vaccines, many children died of diseases vaccines prevent, like whooping cough, measles, and polio. Those germs still exist today, but children are now protected by vaccines and so we do not see these diseases as often.

For more information

  • Contact the National Immunization Program, CDC:
    National Immunization Hotline:
    English (800) 232-2522    or  Spanish (800) 232-0233
  • Visit the Every Child by Two website:

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This page last modified on July 29, 2004


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