|
First Vaccine to Prevent Cervical Cancer
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.
 |
|
Cervical cancer under the microscope.
Photo
courtesy of NIH’s National Cancer Institute. |
|
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.
|
