A Shot in the Arm for Cancer Prevention

Potential controversy over vaccinating girls against the sexually transmitted human papillomavirus (HPV) simmered in the media for months, but never quite came to a boil.

The vaccine’s demonstrated efficacy in preventing cervical cancer and genital warts caused by HPV ultimately outflanked concerns that its availability might encourage sexual activity; in June, to more fanfare than uproar, the FDA approved the vaccine Gardasil.

Gardasil is highly effective against four strains of HPV, including types 16 and 18 that are responsible for about 70 percent of cervical cancers. (Cervarix, which also targets types 16 and 18, is expected to hit the market by early 2007.)

The Centers for Disease Control (CDC) now recommends that the HPV vaccine be routinely given to girls 11 to 12 years old, and on the strength of the CDC endorsement Medicaid and many insurance companies are covering the cost.

The introduction of the vaccine has big implications for national and world health.

“In developing countries that have not been able to implement cervical cancer screening programs, the vaccine really provides an alternative,” says Evan R. Myers, MD, MPH, chief of clinical and epidemiological research in Duke’s Department of Obstetrics and Gynecology.

“In countries that already have screening in place, as you reduce the incidence of precancer and cervical cancer through vaccination, you shouldn’t need to screen as often and may be able to start screening at a later age.”

Reduced Need for Screening

Reducing screening is important from a cost perspective, but it’s also “a quality of life issue,” according to Shalini Kulasingam, PhD, research associate in obstetrics and gynecology and senior fellow at Duke’s Center for Clinical Health Policy Research.

“With screening you have a lot of opportunities to have the disease detected at a precancer stage and treated. However, studies show that having an abnormal Pap smear can be stressful for women.”

In addition to the patient’s emotional distress, she points to growing evidence that some of the treatments for high-grade precancer may increase a woman’s risk of preterm birth via premature rupture of membranes.

Because we screen frequently in the U.S., and because it’s not known which cases of cervical precancer, or dysplasia, will go away and which will develop into cancer, a lot of women may be getting treatment they don’t need.

“Very few women infected with HPV go on to develop any abnormalities at all,” says Myers, “and most who do never develop cancer.”

Myers and Kulasingam, who co-authored a 2003 study assessing the cost-effectiveness of HPV screening program strategies, expect that ultimately an effective vaccine will enable women to screen less frequently and perhaps delay their initial screening.

“Every model we’ve looked at so far consistently indicates we should be able to reduce screenings and have the same or even better outcomes at lower cost with the vaccine,” says Myers. “But until there are longer term data about length of protection, there won’t be any major shifts.”

Good for the Gander?

While the vaccine is not currently approved for use in males, that possibility is being explored. FDA and CDC sought safety data on males, and Merck is doing an efficacy study.

“Because you need both men and women to transmit the disease, you could potentially reach herd immunity faster,” says Myers. “But there may be ethical issues in vaccinating one population solely for the benefit of another. However, Gardasil protects against the strain of HPV that causes genital warts, and that’s of direct benefit to men.”

The vaccine’s effectiveness in men will be harder to demonstrate because, as Myers observes, “Men don’t get Pap smears.”

The Upshot: HPV Vaccination and Screening

• The vaccine Gardasil is recommended for females ages 11 to 26 and deemed safe for girls as young as nine.

• Vaccination is most effective before the onset of sexual activity, but is recommended regardless of sexual history.

• Until more data are available about the vaccine’s duration, current Pap test recommendations are still in place.

• American Cancer Society guidelines suggest women begin cervical cancer screening about three years after they begin having vaginal intercourse, but no later than age 21.

• Screening should be annual with the regular Pap test or every two years with the newer liquid-based Pap test.

• At age 30, women who have had three normal Pap test results in a row may reduce screenings to every two to three years.