HPV vaccine may prevent 70% of invasive cervical ca cases; phase III trials.(Gynecology)

OTTAWA -- A tetravalent human papillomavirus vaccine now in international phase III trials is expected to prevent up to 70% of invasive cervical cancers, Dr. Laura A. Koutsky said at a congress of the International Society for Sexually Transmitted Disease Research.

The vaccine also may prevent up to 90% of cases of genital warts, and its introduction is likely to have a "quick impact" on the rates of warts in the general population, she said.

More than 30 strains of human papillomavirus (HPV) can infect the human genital tract. Most are benign, but oncogenic strains can cause not only cervical and anal cancer, but probably vulvar and penile cancers as well, Dr. Koutsky said.

Strains of the virus targeted by the investigational vaccine are HPV types 6, 11, 16, and 18.

Strain 16 is the most commonly associated with cervical cancer and high-grade intraepithelial neoplasias. A phase II study of a vaccine that targets that strain alone is nearing completion, said Dr. Koutsky, professor of epidemiology at the University of Washington, Seattle.

In the phase II study, which included 2,392 young women, the incidence of persistent HPV-16 infection in those who received active vaccine was 0/100 woman-years by a median of 17.4 months after the three-dose vaccine regimen was completed (N. Engl. J. Med. 347121]:1645-51, 2002). Among placebo recipients, the incidence was 3.8/100 woman-years. Researchers are now following subjects up to 48 months.

There have been 41 cases of HPV infection in the phase II study, all of which were in placebo recipients. Two patients did not seroconvert.