In the United States and other developed nations, the screening test for cervical cancer, the Pap smear, is so widely administered that the disease is fairly rare. Not so in poorer parts of the world, where there's no money for the simple screening test, and thus no way to catch suspicious cells in the cervix before they progress to cancer. The disease, which kills about 280,000 women each year, is caused by one of many varieties of human papillomavirus—a common sexually transmitted virus that, in some women, doesn't go away by itself but leads to cancer. Researchers have long hoped to find a vaccine protecting against HPV infection, since it could easily be administered to women in many different economic circumstances, and several are being tested.

What the researchers wanted to know: Will a new injectable vaccine protect women from HPV-16 and HPV-18, the types of the virus responsible for 70 percent of cervical cancers?

What they did: Researchers led by scientists at Dartmouth-Hitchcock Medical Center and Dartmouth Medical School gave three doses of either the vaccine or a placebo to 1,113 healthy, uninfected women in the United States, Canada, and Brazil over the space of six months. They followed up with the women in 27 months to see if they had contracted HPV.

What they found: Of the 366 women who took all three doses of the vaccine and participated in all follow-up studies, none contracted HPV, compared with 47 of the 355 women who received the placebo and also adhered to follow up. The vaccine was only slightly less effective in women who missed a dose or a follow-up visit; it worked 95 percent of the time in protecting the group receiving the vaccine from persistent viral infection. There were no serious side effects

What the study means to you: The vaccine is being studied for potential approval by the FDA, and this was only the second of three testing phases. The next round will study more women. If the vaccine eventually makes it to market, however, the implications are huge. The authors suggest it would be cost effective to give a vaccine to young teenagers. And eliminating cases of HPV would reduce the number of subsequent false positives from Pap smears, which require more invasive follow-up studies and produce a lot of anxiety.

Caveats: The study was funded by the vaccine's developer, GlaxoSmithKline Biologicals, but the author isn't paid or employed by the company and had full access to all information from the study. Also, in addition to the need for larger and longer-term studies, there are other questions about how the vaccine might be administered. Up for discussion: At what age should the vaccine be given? Since HPV is sexually transmitted, should boys get the vaccine too? Is a booster shot required?

Find out more: For more information on cervical cancer, go to the National Cervical Cancer Coalition.

Read the article: Harper, DM et al. "Efficacy of a Bivalent L1 Virus-like Particle Vaccine in Prevention of Infection With Human Papillomavirus Types 16 and 18 in Young Women: a Randomized Controlled Trial." Lancet. Nov. 13, 2004, Vol. 364, pp. 1757-65.

Article online: www.thelancet.com