Related Pages What Is a Clinical Trial? 1 A basic description of the reason for, and the kinds of, clinical trials. Cancer Vaccines 2 Cancer vaccines are intended either to treat existing cancers (therapeutic vaccines) or to prevent the development of cancer (prophylactic vaccines). Fact Sheet 7.56

What is a Vaccine?
What are Cancer Vaccines?
Substances Used to Make Vaccines

What Is a Vaccine?

A vaccine is a substance designed to stimulate the immune system to launch an immune response. This response is directed against specific targets, or antigens, that are part of the vaccine. An antigen is any substance that the immune system recognizes as foreign.

The flu vaccine, for example, contains copies of the flu virus that cannot cause the flu. Antigens on the viruses in the vaccine stimulate the immune system to produce cells that can fight the flu virus if it shows up in your nose or throat.

The flu vaccine only works if it is given at least two weeks before exposure to infectious flu virus. The immune system needs those two weeks to produce immune cells that can attack the flu virus.

Because the flu virus changes from year to year, a new flu vaccine is needed every year. Your immune system, however, still protects you against last year's flu type. This type of vaccine is called a preventive vaccine - it stimulates a long-lasting immunity that helps protect you from getting sick for years or even for a lifetime.

What Are Cancer Vaccines?

Cancer vaccines are intended either to treat existing cancer or to prevent the development of cancer. Cancer treatment vaccines are designed to strengthen the body's natural defenses against a cancer that has already developed. These vaccines may stop an existing tumor from growing, stop a tumor from coming back after it has been treated, or eliminate cancer cells not killed by previous treatments.

Cancer preventive vaccines are given to healthy people and are designed to target infectious agents that can cause cancer. The HPV vaccine is an example of a cancer preventive vaccine. It is used to help prevent cervical cancer.

Substances Used to Make Vaccines

Vaccines can be made using specific types of molecules from viruses or cells, including molecules from bacterial cells or human cells. These molecules may contain a single antigen or several different antigens. Carbohydrates (sugars), proteins, and peptides (pieces of proteins) are among the types of molecules that have been used to make vaccines. Molecules of DNA or RNA that contain genetic instructions for one or more antigens can also be used as vaccines (for more information, see Cancer Vaccine Strategies ³.)

In addition, whole viruses or cells, or parts of viruses or cells that contain different types of molecules, can be used to make vaccines. The flu vaccine, for example, is made using inactive whole flu viruses. If whole human cells are used as vaccines, they are usually treated with enough radiation to keep them from dividing (growing and multiplying) or enough to kill them.

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Glossary Terms

The molecules inside cells that carry genetic information and pass it from one generation to the next. Also called deoxyribonucleic acid.

The activity of the immune system against foreign substances (antigens).

The smallest particle of a substance that has all of the physical and chemical properties of that substance. Molecules are made up of one or more atoms. If they contain more than one atom, the atoms can be the same (an oxygen molecule has two oxygen atoms) or different (a water molecule has two hydrogen atoms and one oxygen atom). Biological molecules, such as proteins and DNA, can be made up of many thousands of atoms.

A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.

One of the two types of nucleic acids found in all cells. In the cell, RNA is made from DNA (the other type of nucleic acid), and proteins are made from RNA. Also called ribonucleic acid.