Medicine usually progresses in incremental steps. One antidepressant or cholesterol-lowering drug follows another with only marginally improved therapeutic benefit. Vaccines are different. Disease prevention through immunization, whether for polio or mumps, has the potential to transform medical practice, sometimes eliminating illness altogether. Smallpox is now (we hope) confined to heavily protected freezers in Russia and at the Centers for Disease Control and Prevention in Atlanta.

Vaccine developers appear to be on the verge of another remarkable achievement. Two vaccines that are nearing approval by the Food and Drug Administration in the U.S.--one from Merck, the other from GlaxoSmithKline--have demonstrated in clinical trials that they can prevent infection from the two types of the human papillomavirus (HPV) that account for up to 70 percent of cervical cancers. That could make a big dent in a disease that is the second most common malignancy affecting women worldwide and that kills more than half of its victims. In the U.S., in excess of 10,000 women contract invasive cervical cancer annually and nearly 4,000 die of the disease.

The public health community needs to ready itself now for a task as imposing as developing the vaccine. It must convince millions of parents to get their children vaccinated against a sexually transmitted disease. Many youths contract HPV within a few years of their first experience, often in their early teens.

That means that the best time to administer the vaccine is probably between the ages of 10 and 12, when children are less likely to have had sex and when they are scheduled to get boosters for chicken pox, measles and the like. The Merck vaccine also protects against two other types of HPV that cause almost all genital warts, an incentive to get boys immunized, too.

A public health campaign to vaccinate 11-year-olds against STDs will assuredly be a delicate undertaking. A survey that appeared in late November 2005 in the Journal of Adolescent Health noted that half of the 513 physicians polled thought that parents would resist immunizing a child against an STD. Physicians also fretted about parents' perceptions of vaccine safety, with 71 percent saying that those concerns could prove a barrier to vaccination.

Worries about antivaccine barnstorming by religious conservatives may be overblown, however. Although some conservatives think that the vaccine will undercut their "abstinence is best" mantra, others have understood that immunization does not exclude a personal decision to refrain from having sex.

Political agendas should be set aside on this one for the sake of public health. The CDC's Advisory Committee on Immunization Practices, which compiles the national list of recommended vaccines, should give Merck's Gardasil and Glaxo's Cervarix its full endorsement. The approval would spur other activity, such as procuring reimbursement from insurers, that would move the vaccine on its way to becoming a routine part of care. And public health officials and drug companies must meet the challenge of mounting a clear and forceful information campaign. The most important message to get across is that this vaccine is a lifesaver and that every child heading into adolescence should get the jab.