HPV vaccine promises to fight cervical cancer

March 20, 2006

A new vaccine that could eliminate the human papillomavirus (HPV) may soon hit the market. Because of HPV's link to cervical cancer, researchers hope the vaccine will become a standard of preventive care for adolescents.

A new vaccine that could eliminate the human papillomavirus (HPV) may soon hit the market. Because of HPV's link to cervical cancer, researchers hope the vaccine will become a standard of preventive care for adolescents.

"Experts know that cervical cancer is caused by HPV," said Susan Crosby, president of Women In Government (WIG), a nonprofit, bipartisan organization of state legislators who address public policy issues. "With the development of preventive vaccines and more sophisticated diagnostic screening, we face an incredible era in which cervical cancer could be eliminated."

Of the more than 100 strains of HPV, two (HPV 16 and HPV 18) have been shown to cause cervical cancer. These strains are considered the most high-risk or oncogenic types of HPV.

GSK announced in November that in clinical trials its vaccine (Cervarix), which contains the two high-risk strains thought to cause at least 70% of cervical cancers, had prevented 90% of new infections and all persistent infections. Merck has announced similar results with its vaccine (Gardasil), which contains the same two high-risk strains of HPV, plus HPV 6 and HPV 11 (responsible for 90% of genital warts cases).

Despite its promising potential, HPV vaccine is not without controversy. HPV is a sexually transmitted disease (STD), and people must be vaccinated years before they become sexually active. For many parents, this could be a moral issue and in some religions or cultures, it may not be accepted at all. Initial target populations would be children ages 11 and 12. Older children and young adults would be next, with catch-up vaccinations. Vaccinating infants is a future consideration, said Koutsky.

Yet HPV is quite common among sexually active adult women. According to the Centers for Disease Control & Prevention, approximately 80% of sexually active women are HPV-infected by age 50. For 90% of those infected women, the virus is naturally cleared by the body and becomes undetectable within two years. Infections that are not eliminated remain dormant in the body and gradually cause cell changes on the cervix that can become cancerous. The American Cancer Society recommends that women begin annual Pap tests by age 21 or within three years after they begin having sexual intercourse. Pap tests detect abnormal cell changes.

Marketing the vaccine to pediatricians and parents may prove a challenge. "The [drugmakers] will likely shy away from the stigma of cervical cancer as an STD. But they will definitely link HPV with cervical cancer. Thus the vaccine will be promoted as a cancer preventive," said Medford, N.J, pediatrician Charles Scott, M.D., immediate past president of the New Jersey chapter of the American Academy of Pediatrics.

Another stumbling block is that patients will not see immediate benefits for perhaps 20 to 30 years.

Much discussion at the meeting touched on whether the vaccine should be administered to males as well as females. Data on the HPV vaccine efficacy in men are not yet available. "I would make a push for both [genders], but we have a fairly conservative administration and it may want to require this vaccination for girls only because it is ultimately a cancer preventive," Scott said.

Whether the vaccine becomes a standard of preventive care for children rides on its acceptance by practitioners and parents. Noted Koutsky, "The promise of such vaccines will be realized only if immunization programs achieve wide coverage."

Scott is optimistic about the future of the HPV vaccine, recalling similar difficulties in getting the chicken pox (varicella) vaccine accepted in the 1990s. Good public relations and consumer education about the dangers of chicken pox (and the fact that parents would not lose time from work to stay home with a sick child) eventually earned its acceptance. The safety of the chicken pox vaccine, licensed in 1995, was also proven over time, said Scott, who predicts a similar outcome for the HPV vaccine.

THE AUTHOR is a writer in the Atlanta area.