We have nearly eradicated many serious and deadly diseases such as measles, mumps and polio thanks to the widespread use of vaccines. Researchers are now working hard to also developing vaccines to treat or prevent cancer. If you or a loved one has cancer, or you are at higher risk for developing cancer, here's the low down on cancer vaccines.

Vaccines prevent disease by using weakened or dead cells from viruses, bacteria or germs to trigger an immune response in your body. In someone who has cancer, his or her immune system does not recognize cancer cells as foreign and therefore doesn't attack them.

Cancer vaccines fall into two categories: prevention and treatment.

Cancer prevention vaccines

To date, the Food and Drug Administration (FDA) has approved two cancer vaccines, one for the hepatitis B virus, which can cause liver cancer, and the other for the human papillomavirus (HPV), which causes about 70 percent of all cervical cancers. Cancer prevention vaccines target viruses implicated in cancer, not cancer cells.

You may be familiar with Gardisil, the highly marketed and controversial cancer prevention vaccine for HPV. The FDA approved it in 2006. European physicians administer another HPV vaccine, which the FDA has not approved in the United States.

Cancer treatment vaccines

You may wonder how a vaccine can prevent a disease you already have. Cancer treatment vaccines prevent cancer from returning after treatment by mobilizing your immune system to attack cancer cells. Cancer treatment vaccines may also improve how your body responds to conventional cancer therapies. They can even attack cancer cells when delivered directly to the tumor via a gene.

Scientists are developing cancer treatment vaccines. At the June 2009 meeting of the American Society of Clinical Oncology, for example, researchers reported on the progress of a new treatment vaccine for melanoma (skin cancer). In the study, doctors administered the vaccine right along with the standard cancer treatment. The tumors in one out of four patients with advanced melanoma shrunk following treatment. Researchers recommend additional studies to support these early, but encouraging, results.

The National Institutes for Health are conducting numerous clinical trials on both cancer prevention and cancer treatment vaccines, so it's likely we will see the FDA approve new cancer vaccines in the next few years. If you're interested in participating in cancer vaccine clinical trials, see the complete list of studies at www.clinicaltrials.gov.