Vaccines for HPV and Cervical Cancer
See also our fact sheet on Cervical Cancer and Pap Smears
Human Papilloma Virus (HPV) is the most common sexually transmitted infection in the United States. There are more than 30 known types of HPV viruses that can be passed through sexual contact; while most are harmless, some increase the risk for cervical cancer. Worldwide, 70 percent of all women who get cervical cancer have been infected with either HPV-16 or HPV-18, but not all women who become infected with those types will get cervical cancer. Screening to identify pre-cancerous conditions and treatment can prevent cervical cancer from ever developing. The women who are most likely to get cervical cancer are those who have a difficult time getting health services and therefore don?t receive screening or early treatment.
Worldwide, there are about 500,000 new cases of cervical cancer each year, and about 250,000 deaths. Almost 80 percent of these cases occur in the developing world, where few countries have the health care infrastructure to provide regular screening and preventive services and where cervical cancer is the leading cause of cancer-related deaths in women. In the United States, the numbers are much lower with about 11,000 new cases of cervical cancer every year and between 3,500-4,000 deaths. But it's important to note that the women in this country whose health is most threatened by cervical cancer are women of color: Vietnamese Americans have the highest rate of any racial or ethnic group, with five times more cervical cancer than white women; Mexican American and Puerto Rican women are two to three times more likely to get it than white women; and African-American women's cervical cancer mortality rate is more than double that of whites.
Two vaccines to prevent cervical cancer have been developed. GlaxoSmithKline has a vaccine called Cervarix that protects against several strains of HPV that can cause cervical cancer, including HPV-16 and HPV-18; Cervarix is not yet available in the United States, but GSK expects it will be soon. Merck has developed a vaccine known as Gardasil which also prevents infection with HPV-16 and HPV-18, as well as offers protection against other types of HPV that cause genital warts. This vaccine received FDA approval in June 2006 and distribution has begun. There is also preliminary data showing that both vaccines might protect against other strains of HPV as well, which means they could potentially offer greater protection. Research shows the vaccines to be most effective when they are administered before sexual activity has begun to eliminate the chance that HPV infection may already have taken place. The Centers for Disease Control, the American Academy of Pediatrics and the American Academy of Family Physicians recommend that the HPV vaccine be included as part of routine medical care for girls between 11 and 12 years old, with catch-up administration recommended for girls 13-18.
Based on the research that Merck has made public to date, its vaccine appears to be highly effective and very safe. While the National Women's Health Network (NWHN) supported approval of the Merck vaccine by the Food and Drug Administration (FDA), it is important to acknowledge that it is a new technology and clinical experience with it is limited. Merck studied the women in its trials for more than two years, but since the time between when a woman gets infected with HPV and when she develops cervical cancer is usually decades-long, there are some questions about the effectiveness of the vaccine that cannot yet be answered. And, as with any new product, there isn?t any data about its long-term safety.
The NWHN also notes that the vaccines alone will not substantially reduce the incidence of cervical cancer in the United States. It's critical that we continue to support and promote cervical cancer screening programs, even for women who have been vaccinated, since the vaccines do not offer complete protection.
Reducing the Incidence of Cervical Cancer
Although the new HPV vaccines significantly decrease a woman's chance of developing cervical cancer, neither offers 100 percent protection against all cervical cancer. Both vaccines protect against the two most common cancer-causing strains: HPV-16 & HPV-18 which cause 70 percent of all cervical cancer cases worldwide. Cervarix also protects against other cancer-causing strains which may increase its ability to protect women. GSK has announced plans to test its vaccine directly in comparison to Gardasil to determine which is more effective.
New research suggesting a possible link between HPV infection and cancers of the mouth and throat has raised the question of whether the vaccines might also protect against other cancer as well. The NWHN believes that HPV vaccines hold the potential to be a significant step forward in cancer prevention for women. However, the potential will only be realized if the vaccines are made accessible to the women who are at greatest risk.
Most cervical cancers develop slowly over many years. Regular pap tests can detect irregular changes in a woman's cervix, and she can have the abnormal tissue removed to prevent cervical cancer from developing. However, women who cannot access health care services - because they don?t have insurance or money to pay for care, must travel long distances to reach a health care provider, or can?t find a provider who speaks their language or understands their cultural concerns - may go many years without being screened or may never be screened at all. Without the early warning from a screening test, it's often not possible to catch the changes in the cervix early enough to prevent cancer from developing.
School Entry Requirements
By May 2007, legislation to make the HPV vaccine a mandated school entry requirement for girls had been introduced in almost half the states, an unusually fast policy response to the introduction of a new health technology. One explanation for this speed is that Merck funded lobbying efforts to advance the policy initiatives. Anticipating that its competitor would be on the market soon, the company had a strong financial incentive to establish its market without delay. Opposition to the mandates has come both from public health advocates concerned that it is too soon to require girls to get a new vaccine and from some conservative activists who argue that vaccinating girls against a sexually transmitted infection will promote promiscuity and condone girls? sexual activity.
The NWHN supports making HPV vaccines accessible immediately to those who want them and including them in school entry requirements over time if evidence of safety and effectiveness continue to be strong as more clinical experience accumulates. It is also important to give state legislators and public health agencies time to allocate appropriate funding to ensure access to the vaccines. The NWHN is opposed singling the HPV vaccine out for special treatment either because of a corporate profit incentive or because of the political agenda of abstinence-only conservatives. If the promise of the vaccines holds up over time, we believe that making them a part of school-entry requirements is likely to be the best way of ensuring that all girls, regardless of economic status or race, will have access.
To make the most effective use of the HPV vaccines, the NWHN urges:
- Merck and GlaxoSmithKline to support initiatives to make both vaccinations and cervical cancer screening available to the women most at risk for cervical cancer - those who face economic, linguistic and other barriers to health care services.
- The FDA to ensure that both companies follow through on promises to conduct follow-up research with the people who participated in previous studies as well as additional safety monitoring of women who are vaccinated. These studies are critical for learning more about the long-term safety and efficacy of HPV vaccines.
- The FDA to mandate product labeling and other mechanisms to communicate a message to both health care providers and patients that even women who are vaccinated should continue to receive regular cervical cancer screening.
For More Information and Resources:
1. National Cancer Institute. Human Papillomaviruses and Cancer: Questions and Answers http://cancernet.nci.nih.gov/cancertopics/factsheet/Risk/HPV
2. Alan Guttmacher Institute. The Public Health Promise and Potential Pitfalls of the World's First Cervical Cancer Vaccine. http://www.guttmacher.org/pubs/gpr/09/1/gpr090106.pdf
3. National Women's Health Network. Fact Sheet on Cervical Cancer and Pap Smears.
Updated May 2007