The first vaccine against cervical cancer will be available to girls as young as nine later this month. Its manufacturer, Merck & Co. Inc., is already taking orders for Gardasil. The three-shot series costs $360.

The newly approved vaccine works by preventing infection by four of the dozens of strains of the human papillomavirus, or HPV, the most prevalent sexually transmitted disease. The Food and Drug Administration licensed it for use in girls and women 9 to 26. It's still being studied in males.

Gardasil protects against the two types of HPV responsible for about 70 percent of cervical cancer cases. The vaccine also blocks infection by two other strains responsible for 90 percent of genital wart cases.

"FDA approval of the HPV vaccine, the first vaccine targeted specifically to preventing cancer, is one of the most important advances in women's health in recent years," said Dr. Carolyn Runowicz, president of the American Cancer Society.

Related Story: 12 Things You Should Know About the Cervical Cancer Vaccine

Click on the video box in the above right corner of this story to watch Dr. Manny Alvarez' report on the new cervical cancer vaccine.

Whether Gardasil enters routine use depends on what the national Advisory Committee on Immunization Practices recommends at a June 29 meeting. The panel's endorsement is critical.

Clinical trials showed Gardasil prevented 100 percent of cervical cancer related to the two HPV strains in women who had not been previously infected, Merck said. It also prevented 99 percent of the cases of genital warts caused by the two other strains.

"Fortunately, we can now include the worst types of HPV and most cervical cancer in the list of diseases that no one need suffer or die from ever again," said Alex Azar, deputy Health and Human Services secretary.

Merck wants to sell the vaccine around the world. Each year, cervical cancer kills an estimated 240,000 women worldwide, including 3,700 in the United States. The incidence of the cancer is lower in the U.S. because Pap tests are so routine.

The vaccine does not eliminate the need for the regular exams, which can detect precancerous lesions and early cancer. Merck has said Gardasil could cut the number of abnormal Pap results due to HPV infection. By age 50, some 80 percent of women have been infected with the virus. In most cases, the body clears the virus.

Research presented earlier suggests a bonus to Gardasil: It also protects against vaginal and vulvar cancers linked to the four types of HPV.

Gardasil works best when given to girls before they begin having sex and run the risk of HPV infection. The vaccine does not protect those already infected.

The FDA said that Gardasil appeared very safe. It remains unclear if its effect is long-lasting or if women will need booster shots later in life. Merck will monitor its long-term effectiveness.

Analysts believe Gardasil sales could top $1 billion a year for Merck. The Whitehouse Station, N.J., company faces thousands of lawsuits over its withdrawn painkiller Vioxx.

Eventually, it could face competition from GlaxoSmithKline PLC, which is also developing its own HPV vaccine.