June 16, 2006

First Vaccine to Prevent Cervical Cancer

a microscopic image of cervical cancer Cervical cancer under the microscopeNIH’s National Cancer Institute.

An estimated 10,000 women in the U.S. will be diagnosed with cervical cancer this year and nearly 4,000 will die from it. Worldwide, it strikes nearly half a million women each year, claiming a quarter of a million lives. Nearly two decades ago, researchers at NIH’s National Cancer Institute (NCI) and other institutions began searching for the underlying causes of cervical cancer. That scientific quest led to last week's approval by the Food and Drug Administration (FDA) of the vaccine GardasilTM, which protects against infection from the two types of human papillomavirus (HPV) that cause the majority of cervical cancers worldwide.

While most HPV infections don’t lead to cancer, researchers discovered that virtually all cases of cervical cancer are caused by HPV infection. NCI scientists Dr. Douglas Lowy and Dr. John Schiller then set out to boost the body's immune response to prevent the cancer-causing infection. This work led to the development of the technology on which the newly approved HPV vaccine is based.

"Genetic engineering — technology involving the manipulation of genetic material — was used to create this vaccine, which is made up of non-infectious virus-like particles," explained Lowy. "These hollow spheres, formed by a single protein from the virus, trigger an antibody response that is capable of protecting the body against infection by the targeted virus types."

The FDA reviewed four studies, one in the U.S. and three multinational, to assess how well Gardasil worked in a total of about 21,000 women between the ages of 16 and 26. In women who had not already been infected, Gardasil was nearly 100% effective in preventing the precancerous lesions and genital warts that are caused by infection with HPV. The studies weren’t long enough for cervical cancer to develop, but preventing cervical precancerous lesions is considered a sign of the prevention of cervical cancer as well. Two other studies looking at the immune responses in the 9-15 year age group support the idea that the vaccine should be effective for younger females as well. Most of the side effects in the studies reviewed by the FDA were mild or moderate local reactions such as pain or tenderness at the site of injection. The manufacturer, Merck & Co., Inc., has agreed to do additional studies to further evaluate safety and long-term effectiveness.

The vaccine is now approved for use in females 9-26 years of age. However, women should continue to be screened with an approved method such as a Pap test, since other forms of HPVs that aren’t targeted by the current vaccines can also cause cervical cancer.

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