June 16, 2006

Vaccine may guard against cervical cancer

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John Greene, M.D.

Vaccine may guard against cervical cancer

Howard Jones III, M.D.

Howard Jones III, M.D.

Peter Wright, M.D.

Peter Wright, M.D.

A vaccine to protect women against cervical cancer was approved last week by the Food and Drug Administration after a 40-month trial of 4,000 young women at 13 U.S. sites, including Vanderbilt University Medical Center.

The vaccine works by preventing infection by four strains of the human papillomavirus, (HPV), the most common sexually transmitted disease. About 20 million people are believed to be infected with HPV, according to the National Institute of Allergy and Infectious Diseases.

The Vanderbilt portion of the study, led by principal investigator Peter Wright, M.D., enrolled 51 young women between the ages of 16 and 26, mostly Vanderbilt undergraduate students who were recruited by John Greene, M.D., director of the Zerfoss Student Health Center.

The vaccine, Gardasil, manufactured by Merck & Co. Inc., protects against Types 16 and 18, the two types of HPV responsible for about 70 percent of cases of cervical cancer cases. Although many women are infected with HPV, their normal immune defense mechanisms get rid of the virus, and most women never go on to have an abnormal Pap smear or cervical cancer. The vaccine boosts this natural immunity, completely preventing the viral infection.

The vaccine also blocks infection of two other strains of HPV, responsible for 90 percent of genital warts cases.

The women who participated in this trial had not been exposed to HPV. Half were vaccinated with the HPV vaccine and half with a placebo. They were followed up in six-month intervals with clinic visits and Pap smears, and those with abnormal smears were evaluated further with colposcopic evaluations or biopsies.

“Over the past 15 years, there has been increasingly clear evidence that cancer of the cervix is caused by a virus,” said Howard Jones III, M.D., director of Gynecologic Oncology and one of the study's investigators.

“We've been able to identify over time that it's the HPV virus that causes cervical cancer, but we've never been able to prevent it. This vaccine allows us, for the first time, to prevent the infection of HPV in women.”

Wright said he is “enormously pleased” about the promise of the vaccine.

“It's a safe, very effective vaccine. As with any vaccine there are still things unknown, primarily because cervical cancer develops a long time after the initial HPV infection. But we know that the HPV infection is amazingly blocked by this vaccine. We don't know if this would be effective if another strain of HPV took its place, but that hasn't happened much in vaccines. These are all pretty much hypothetical concerns.”

The next step is to see if the vaccine works in the general population, to make sure there are no side effects, and that it's effective in larger groups of people, Jones said. “But it is still important that women continue to get their regular Pap smear screening. Even if everyone is being vaccinated 15 years from now, we still might have 30 percent of the current number of women with cervical cancer because the current vaccine is directed against only the two most common types of HPV which cause 70 percent of cervical cancer. In addition, the progression from HPV infection to cervical cancer is slow, and women may already be infected but not develop an abnormal Pap smear for several years.”

There are 9,500 new cases of cervical cancer each year in the United States, and almost 50,000 cases a year of cervical dysplasia. Cervical cancer kills about 240,000 women in the world each year, and about 3,500 in the United States alone.

Although the vaccine will most likely be marketed as a cancer vaccine, rather than a sexually transmitted disease vaccine, its effectiveness against genital warts may be an important advantage to patients, Jones said. “The onset of infection with virus to cancer is probably five to 10 years. The onset of genital warts is six to eight weeks. That's a much more prompt and visible process, and warts affect men too.”

The vaccine is not inexpensive, costing $360 for the three doses that are required — the initial dose; the second, two months after the first; and the third, four months after that.

The FDA has approved the vaccine's use in girls and young women 9 to 26 who test negative for the virus and are without cervical dysplasia. Vanderbilt is currently working on a policy about whom the vaccine would be recommended to in its ob/gyn patient population when the vaccine is available here sometime after July 1, Jones said.

“We spend an awful lot of money evaluating and treating patients with cervical dysplasia,” Jones said. “There's a lot of excitement here, especially among those of us who have been involved in testing this vaccine.”

Wright is professor of Pediatrics, Microbiology and Immunology and Pathology, and director of the Division of Pediatric Infectious Diseases.