Vaccines help prevent people from getting sick. They also help reduce the spread of disease to others and prevent epidemics. There are many kinds of vaccines. Each vaccine is made up of parts of weakened or killed bacteria or viruses of a specific disease. After you have a vaccine, your body's immune system, Opens dialog makes antibodies, Opens dialog to fight the disease. If you are exposed to the same disease in the future, the antibodies kill the bacteria or viruses before they have a chance to make you sick.

If you get a vaccine, it may not completely prevent you from getting a disease, but it makes it much less likely. If you get a disease even after you have been vaccinated, it usually will be only a mild case.

Vaccines are usually given by shot (injection). Some are given by mouth as a pill or liquid, or by a spray (aerosol) into the nose. Vaccines are also called immunizations.

In the United States, the Centers for Disease Control and Prevention (CDC) and other national organizations advise people about which immunizations, Opens dialog they should get and when. Immunization schedules are for healthy children, teens, and adults as well as for people who have health problems and other circumstances, including pregnancy, asthma, or diabetes. To see or print a list of recommended immunizations based on your age, past immunization history, and other factors, see the CDC immunization schedules at www.cdc.gov/vaccines/schedules/index.html.

Children and teens in the United States usually need proof that all their immunizations are up-to-date before they can start school or day care. Also, students of any age entering college usually need to have a written record showing that their immunizations are up-to-date.

For more information on when to get vaccines, see the topic Immunizations.

The CDC may recommend certain immunizations for people who are going to travel to a foreign country. For more information, see the topic Travel Health.