A vaccine for cervical cancer.

In a preliminary study, a vaccine against a virus that can cause cancer has proved 94 percent effective in women. The success sets the stage for an enhanced version of the vaccine and the massive trial needed for government approval of the final product, which is intended to protect against the human papillomavirus (HPV).

Some HPV strains cause cervical cancer, while others are responsible for genital warts (SN: 11/23/02, p. 323; 3/3/01, p. 132). In the new trial, researchers gave 768 young women three injections of the vaccine, and 765 similar women three placebo shots. Over the following 3.5 years, only 7 women who were vaccinated developed an HPV infection, compared with 111 of those getting the inert shots, says Constance Mao of the University of Washington School of Medicine in Seattle.

An HPV infection can lead to aberrant cervical-cell growth, the kind detectable on a Pap smear. If not removed, the cells can progress to precancerous lesions and sometimes cancer. In this trial, none of the vaccinated women developed such aberrant cell growth, whereas 24 of those receiving the placebo did, Mao said.

Merck Research Laboratories of West Point, Pa., has created the enhanced vaccine using proteins from four HPV strains--two that cause cancer and two that cause genital warts. Researchers have enrolled 25,000 men and women worldwide for this vaccine's large-scale test.--N.S.