HPV vaccine research yields promising results

What if you could offer your patients a vaccine for protection against human papillomavirus (HPV), a sexually transmitted disease (STD) that can cause genital warts and cervical cancer? Just-published results from a randomized double-blind study indicates that an investigational vaccine developed by West Point, PA-based Merck & Co. reduced the incidence of human papillomavirus type 16 (HPV 16) infection in 100% of women who previously had not been infected with the STD.1

According to the Research Triangle Park, NC-based National HPV and Cervical Cancer Preven-tion Resource Center, there are more than 70 HPV types. About 30 of these types are sexually transmitted and cause genital HPV. HPV infections account for about one-third of all new STD infections; about 20 million people are thought to have an active HPV infection at any given time.2

The investigational vaccine studied in the published paper is a monovalent vaccine intended to prevent infection by HPV 16. Of the more than 30 types of HPV known to infect the human genitalia, HPV 16 is the most commonly linked with cancer since it is present in 50% of cervical cancers.3

The monovalent vaccine is just one component of Merck’s vaccine investigation, says Kelley Dougherty, manager of Merck-Vaccine public affairs. The company is pursuing investigation of a multivalent vaccine looking at HPV 16, 18, 6, and 11, she reports.

Because cervical cancer involves multiple HPV types, it is important to have a vaccine that will provide coverage for more than one type, says Laura Koutsky, MSPH, PhD, professor of epidemiology at the University of Washington in Seattle and lead author of the published paper. By including HPV 16, found in 50% of invasive cervical cancers, and HPV 18, identified in about 20% of cancers, such a vaccine could prevent up to 70% of invasive cervical cancers, notes Koutsky. The vaccine also would target HPV 6 and 11, which are associated with genital warts.

Look at the research

In the double-blind study, researchers randomly assigned 2,392 young women ages 16 to 23 to receive three doses of placebo or HPV-16 viruslike-particle vaccine, given at day 0, month 2, and month 6. Genital samples to test for HPV-16 DNA were obtained at enrollment, one month after the third vaccination, and every six months thereafter. Of the women who received the vaccine, 99.7% had seroconversion, and none became infected with HPV-16 after a median follow-up of 17.4 months. The paper includes information from the first two years of the study; the researchers expect to follow the women for an additional two years.

A total of 41 women in the placebo group tested positive for HPV-16 infection during the study; no cases were recorded in the vaccine group. Nine cases of HPV-16-related cervical intraepithelial neoplasia occurred among women who received the placebo; no cases were recorded among women who received the vaccine.

The vaccine generally was well tolerated, and the incidences of adverse experiences were similar between treatment groups, the investigators report. There were no vaccine-related serious adverse experiences, and the overall incidence of nonserious adverse experiences were comparable between treatment groups. The most frequent adverse experiences reported by both women who received the vaccine or the placebo were injection site pain, headache, and injection site redness.

Women seek HPV info

Women are looking for more information on HPV, say officials with the National HPV and Cervical Cancer Prevention Resource Center. Its telephone hotline provides up-to-date information on the virus, risk reduction, diagnosis and treatment, as well as support for emotional issues surrounding HPV such as self-esteem and partner communication. The center launched an HPV Chat Room in March 2002 and has seen an average 200 users per month. Its HPV e-mail service responds to some 150 queries each month.

HPV infection is a chronic condition, even when it is asymptomatic. No therapy has been shown to eradicate the virus. For treatment of genital warts caused by HPV, providers can choose from cryotherapy; application of podophyllin; application of trichloracetic acid; or surgical removal via scissors, shaving excision, or electrocautery. Other provider-administered treatments include laser surgery or intralesional interferon. Patient-administered prescription treatments include podofilox gel (Condylox, Oclassen Pharmaceuticals, a division of Watson Pharmaceuticals, Corona, CA) and imi-quimod cream (Aldara, 3M Pharmaceuticals, St. Paul, MN). (Contraceptive Technology Update reported on genital wart treatments in April 2002; see "Examine genital wart treatment options," p. 43.)

The promise of an effective vaccine against multiple HPV types is exciting, but much research must be conducted before a vaccine reaches the marketplace, says Koutsky.

"These are very promising results, but the bottom line is that until a vaccine is fully tested and available, the best way to prevent cervical cancer is to participate in routine Pap screening," she states.

References

1. Koutsky LA, Ault KA, Wheeler CM, et al. A controlled trial of a human papillomavirus type 16 vaccine. N Engl J Med 2002; 347:1,645-1,651.

2. National HPV and Cervical Cancer Prevention Resource Center. HPV: Get the Facts. Accessed at: www.ashastd.org/hpvccrc/quickfaq.html.

3. Merck & Co. Primary analysis at two years shows that investigational vaccine reduced incidence of infection with HPV 16 and HPV 16-related pre-cancer of the cervix. Press release. Nov. 20, 2002. Accessed at: www.merck.com/newsroom/press_releases/112002.html.

Resources

The National HPV and Cervical Cancer Prevention Hotline offers free information to the public about risk reduction, diagnosis and treatment of HPV and the prevention of cervical cancer, including the most up-to-date Food and Drug Administration-approved technologies. Trained health communication specialists are available to address questions related to transmission, prevention, and treatment of HPV. The hotline is open from noon to 7 p.m., EST, Monday through Friday. Telephone (919) 361-4848.

To access the e-mail service and HPV chat room offered by the National HPV and Cervical Cancer Prevention Resource Center, go to the American Social Heath Association web site, www.ashastd.org; click on "Programs and Resource Centers," then "HPV Resource Center." At the center web page, click on either "HPVnet Email Account" or "HPV Chat Room."