WASHINGTON, June 8 — Federal drug officials on Thursday announced the approval of a vaccine against cervical cancer that could eventually save thousands of lives each year in the United States and hundreds of thousands in the rest of the world.

The vaccine, called Gardasil, guards against cancer and genital warts caused by the human papillomavirus, the most common sexually transmitted disease. It is the culmination of a 15-year effort that began at the National Cancer Institute and a research center in Australia, and health officials described the vaccine as a landmark.

Federal vaccine experts are widely expected to recommend that all 11- to 12-year-old girls get the vaccine, but its reach could be limited by its high price and religious objections to its use.

Merck, Gardasil’s maker, said a full, three-shot course would cost $360, making Gardasil among the most expensive vaccines ever made.

“This is a huge advance,” said Dr. Jesse Goodman, director of the Food and Drug Administration’s biologics center. “It demonstrates that vaccines can work beyond childhood diseases to protect the health of adults.”

The vaccine prevents lasting infections with two human papillomavirus strains that cause 70 percent of cancers and another two strains that cause 90 percent of genital warts. But if girls have already been exposed to those strains, the vaccine has no effect, so health experts want the vaccine given before girls have sex. The median age at which girls have sex is 15.

A Merck spokeswoman said Gardasil, which was approved for girls and women ages 9 to 26, would be available in doctors’ offices by the end of June.

The vaccine is not approved for use in boys, although Merck hopes one day to change that. If the company is successful, analysts expect that sales could surpass $4 billion by 2010.

Cervical cancer is the second-leading cause of death in women across the globe, affecting an estimated 470,000 women and killing 233,000 each year. Widespread use of Pap smears has reduced its toll in richer nations. In the United States, about 9,710 women contract cervical cancer each year, and some 3,700 die.

Private health insurers are likely to cover the vaccine for 11- and 12-year-old girls, although older women may have to pay for it themselves.

Vaccines are one of the most cost-effective medical interventions available. But Gardasil’s price could put it out of reach for most women in poor countries and some in the United States who lack private insurance.

A federal program is expected to provide the vaccine to 45 percent of the children in the United States for whom it is recommended. But state programs that cover other children are having trouble buying other expensive vaccines.

North Carolina, for instance, spends $11 million annually to provide every child with seven vaccines. Gardasil alone would probably cost at least another $10 million.

“Increasingly, states are asked to make a Sophie’s choice about which diseases they will allow children to be hospitalized or killed by,” said Dr. Paul Offit, director of infectious diseases at Children’s Hospital of Philadelphia.

Liberals in Congress and elsewhere have warned that the Bush administration and religious groups should not interfere with Gardasil’s approval or required use.In response, many conservative groups have made statements supporting the vaccine.

“Despite rumors to the contrary, our organization doesn’t oppose the vaccine and we have taken no position regarding mandatory laws,” said Wendy Wright, president of Concerned Women of America, a conservative group based in Washington.

Some groups support the vaccine but oppose mandatory vaccinations because cervical cancer is caused by a sexually transmitted virus.

“We can prevent it by the best public health method, and that’s not having sex before marriage,” said Linda Klepacki of Focus on the Family, a Christian advocacy organization based in Colorado Springs.

But scientific and budgetary issues are much more likely to determine Gardasil’s uptake. Three shots must be given over six months. Such a schedule is routine among infants, but preteens are tougher to corral into doctors’ offices.

An independent panel formed by the Centers for Disease Control and Prevention is scheduled to decide June 29 who should get the vaccine.

The panel is expected to recommend vaccinations for all 11- to 12-year-old girls, while agreeing that girls as young as 9 or women as old as 26 can get the vaccine if they wish. It is also expected to suggest that states make vaccinations mandatory.

Many states will not have the money to do much more, said Dr. Leah Devlin, state health director for North Carolina and president of the Association of State and Territorial Health Officials.

Already, North Carolina has been unable to provide six federally recommended vaccines to all children because of cost, Dr. Devlin said. The state cannot mandate any vaccine that it does not agree to provide.

In the United States, about 20 million people are infected by the human papillomavirus each year. By the time women reach the age of 50, 80 percent have been infected.

Most infections are quickly dealt with by the immune system. But some strains cause changes in cells that line the cervix in some women. The changes years later can turn into cancer. Most patients contract the disease in their 40’s and 50’s.

GlaxoSmithKline, based in London, is also developing a vaccine against cervical cancer that it expects to submit for F.D.A. approval at the end of the year.

Pap smears can detect precancerous changes to the uterus, but the tests are sometimes wrong, missing some cases and leading to unnecessary procedures in others. Because Gardasil protects against only four viral strains and its effects in those four will take decades to have widespread effect, health officials are recommending that women continue to undergo routine Pap tests.

Silvia Ford, a 35-year-old stay-at-home mother from Maryland, learned in November 2004, just three months after bearing her second child, that she had cervical cancer. Surgeons removed her uterus, for which she has no regrets. “I wanted to be around to take care of the two children I’ve already got,” she said.

Ms. Ford is checked every three months for signs of cancer. She plans to have her daughter, now 6, vaccinated at some point.

“This vaccine should not lead to an argument about when girls have sex,” Ms. Ford said. “It’s about saving the lives of women in their child-bearing years, letting them have children or take care of the children they already have.”

Merck had originally hoped to get the vaccine approved for use in boys. But although women have routinely allowed swabs to be taken of their vaginal cells, the company found that men rebelled against the use of emery boards to collect cells from their penises. Researchers eventually discovered that jeweler’s-grade emery paper effectively removed cells without alarming men and were able to complete their studies.