Sexually Transmitted Infections
Gardasil: What you need to know about the HPV vaccine
Pap tests still the best tool in preventing cervical cancer
This perspective on Gardisil was written by the Canadian Women's Health Network.
Cervical cancer is caused by persisting infection with a sexually transmitted virus called the human papillomavirus (HPV). There are over 100 types (strains) of HPV. About 35 types of HPV infect the genitals and reproductive organs. Within these 35, there are high-risk and low-risk types of HPV.
High-risk HPV infections that persist cause cancer when other factors are also present (for example, having a stressed or compromised immune system, poor nutrition or smoking). The low-risk HPV infections have a less-frequent association with cancer but do cause genital warts. Genital warts are similar to warts on other parts of the body, and are usually treated with liquid nitrogen or are surgically removed; they do not themselves cause cancer.
With a healthy immune system, most people who become infected with HPV can eliminate the virus from their body -- with or without treatment -- within three years (the average is about 9 to 13 months). Most women who get an HPV infection do not develop cervical cancer.
It is important to keep in mind that a compromised immune system, which increases a woman’s risk of cervical cancer, can result from many things, including poverty and poor nutrition. Whether in North America or elsewhere in the world, women who die from cervical cancer are often poor. Efforts to eliminate cervical cancer require understanding and addressing this critical fact.
Gardasil: The HPV vaccine and cervical cancer prevention
Gardasil is the first vaccine against HPV to be approved for use in Canada and the US. This specific vaccine prevents infection from HPV types 6 and 11, which cause genital warts, and HPV types 16 and 18, which cause cancer.
The vaccine is not a treatment or cure for cervical cancer or genital warts, but it does prevent infection by these specific types of HPV if it is administered to girls and women before their first sexual encounter.
Ads about cervical cancer and genital warts now appear in various media. Putting the information about warts and cancer together can be confusing, because some people assume that having genital warts is a risk for cervical cancer. This is not so. In addition, the ads may generate excessive fear by obscuring the fact that cervical cancer affects a relatively small number of women and is rarely fatal in Canada and the US.
The vaccine is also very expensive. It is administered in a series of three injections provided over a six-month period of time, and the cost is approximately $405 Canadian per woman and girl.
If the HPV vaccine is to be covered by the Canadian public health budget, it would be a major additional cost for an already overburdened system. And it is not yet clear that the benefit of this vaccine justifies its very substantial cost. Using public health funds to ensure that all women benefit from regular Pap tests may represent a more effective use of resources in the public sector.
The importance of Pap screening
Pap screening for cervical abnormalities has greatly reduced the incidence of cervical cancer in Canada. Cervical cancer is considered to be 90% preventable with screening and treatment. And Pap screening should be available and accessible to all girls and women, as has been recommended, on a regular basis.
Cervical cancer is responsible for the deaths of about .002% of the female population, or about 400 women per year in Canada. In parts of the world where Pap screening is not available, and where poverty and poor nutrition increase the risks associated with getting – and not being treated for -- cervical cancer, thousands of women die every year from this preventable disease.
If a woman has an abnormal Pap smear that reveals atypical cells, or a low-grade lesion, the body most often repairs itself without treatment. However, a woman with Pap smear results that reveal the possibility of a high-grade lesion, or a woman who already has a high-grade lesion, needs to undergo further testing. She may then have to undergo procedures to remove the abnormal cells. Follow-up testing will indicate if the woman still has abnormal cells that require attention.
Removing abnormal cells prevents invasive cancer in 90% of cases. In North America, many women who show abnormal Pap results – which can be worrisome – do not actually develop cervical cancer.
Since the introduction of the Pap test in Canada, the cervical cancer death rate has dropped by half. In the US, the incidence of cervical cancer fell by 74% between 1955 and 1992.
The HPV vaccine does not eliminate the need for Pap tests, because it does not protect against all forms of cancer-causing HPV infections, and it is not effective if a woman already has the type of virus the vaccine is designed to prevent.
Unfortunately, not all women have access to regular Pap tests. Those who don’t are often immigrants, poor women, Aboriginal women or women in remote areas without access to appropriate health care. Also, women who have sex with women tend to be under-screened because their health care providers incorrectly assume that they do not need this testing. These women are often at higher risk for cervical cancer. However, these same populations of women and girls are less likely to be able to afford an HPV vaccine as well.
Gardasil: HPV vaccine not the only option for addressing cervical cancer prevention
Women are more likely to develop cervical cancer if they have multiple sexual partners or become sexually active at an early age. Women who get the HPV vaccine need to be cautioned about developing a false sense of security about their sexual activity.
An HPV vaccine does not eliminate the need for protected sex or prudence about one’s choice and frequency of sexual partners. Barrier methods of protection (such as condoms) are still necessary to prevent HIV/AIDS and other types of infection not prevented by the HPV vaccine.
The HPV vaccine is most effective if it is first administered before any exposure to the HP virus; that is, before a woman’s or girl’s first experience of sexual activity (with skin-to-skin contact). As a result, the US Advisory Committee on Immunization Practice recommends routine vaccination of 11-12 year old girls. In Canada, the vaccine has been approved for girls and women aged 9-26. However, research on safety and effectiveness conducted to date includes relatively few girls in the younger age category, so current safety data may not be applicable to them.
Some pharmaceutical companies and public health agencies are promoting the use of an HPV vaccine by all women, and by all girls beginning at age nine, as a way to eradicate cervical cancer. However, since Gardasil, the only approved vaccine, protects against the two types of HPV that are responsible for 70% of cervical cancers and not against types of the virus responsible for the other 30% of cervical cancers, "reduction" rather than "eradication" is a more accurate goal. Given this fact, proposals to make the vaccine mandatory may not reflect the best use of public health funds at this time.
Pap screening and HPV tests remain important tools in cervical cancer prevention and these tools still do not reach all the girls and women that they should. The HPV vaccine may also prove to be a useful tool, but we do not yet have the full story on its long-term safety, especially in young girls.
Until we know more about long-term safety and duration of effectiveness of the Gardasil HPV vaccine, as well as about how effective it actually is in reducing cervical cancer rates, health care dollars may be better spent in enhancing Pap screening programs (including Pap registries), and reaching the most marginalized populations (poor women, new immigrants, Aboriginal, rural and remote women) with Pap screening.
End of article.
For more information on the cervical cancer and the HPV vaccine, see:
Written by: Women and Health Protection and the Canadian Women’s Health Network
Last revised: March 2007
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