Pap smear need reduced by HPV vaccine

The greatest accomplishment in the history of public health initiatives, or so your dentist will tell you, was the addition of fluoride to public water supplies—a small amount of fluoride in drinking water dramatically reduces the incidence of cavities. The reasons for this success are simple: Fluoride-treated water is inexpensive and requires no effort on the part of the public, save to drink tap water.

Likewise, Papanicolau (Pap) screening has greatly reduced the mortality rate attributed to cervical cancer in the US and industrialized world (Hanna et al., Calloway et al., Hymel). Although Pap screening is fairly expensive, it is less expensive than treating cervical cancer. Patients with cervical cancer caught at an early stage through the Pap screening have a 100% survival rate over 5 years. In the US approximately 12,000 women a year are diagnosed with cervical cancer with about 4,000 women succumbing to the disease. The benefits of Pap screening are put into stark clarity, however, when worldwide figures are considered. As the second-leading cause of cancer death among women worldwide, cervical cancer affects about 500,000 women a year, half of whom may die of the disease. The lack of regular, or any, access to Pap screening and other medical treatment in the developing world accounts for this disparity.

Nearly all cases of cervical cancer result from a chronic human papilloma virus (HPV) infection. HPV strains 16 and 18 cause 50-60% and 10-20%, respectively, of cervical cancers, with 5 other strains making up most of the remaining 30% of cases (Hanna et al., Hymel). Additionally, strains 6 and 11 have been known to cause genital warts. Altogether approximately 40 HPV strains, or genotypes, affect genital tissue with cervical cancer being the most common resulting cancer. Statistics vary on prevalence of HPV in the US, but some estimate 6.2 million newly-infected persons each year. Studies suggest up to 70% of adults have had an HPV infection; most infections are cleared by the body and do not result in a chronic condition that may progress to cancer. Although a young age at first sexual experience, larger number of sexual partners and lack of condom use correlate with increased risk of HPV infection, infection often occurs soon after becoming sexually active.

Currently two HPV vaccines, Gardasil from Merck and Cervarix from GlaxoSmithKline, are on the market or are soon to be released (Calloway et al.). Gardasil covers both major genotypes involved in cervical cancer and both major genotypes causing genital warts. Cervarix will be used to prevent HPV-16 and -18 infections only, not vaccinating for the strains causing genital warts. Both vaccines were determined by the federal Food and Drug Administration to be completely safe and effective. Currently, recommendations are a series of 3 shots given to women aged 9-26, preferably before first sexual contact (ACS, Calloway et al., Roden et al.). Studies in women older than 26 or women who have had sex and may have had an HPV infection are ongoing and thus it is unknown whether the vaccine will be as effective in these women. Until a treatment for HPV infection is found it remains important for the preventative vaccination to be done before women have any sexual contact. Studies on men have not been prioritized as the incidences of penile or anal cancers are much lower than that of cervical cancer (Dunne et al., Hymel). While women may benefit from men being vaccinated as well it is not clear whether this benefit is beyond that from routine vaccinations of women.

Although Pap screening has been proven to be a tremendous benefit to women’s health, the high prevalence of HPV infections suggest that a relatively inexpensive vaccine series would be extremely valuable (Hanna et al., Calloway et al., Roden et al.). Vaccinations can be given with other childhood vaccinations before sexual contact giving, hopefully, lifelong protection. It is not yet known when or if booster shots will be needed. It is known, however, that Pap screening should be continued as long as the vaccinations do not cover all cancer-causing strains or questions on the length of time of protection given by the vaccine exist, although screening can be done tri-annually instead of every year. It is much easier and less expensive to complete a series of shots once than it is to have annual exams. The peace of mind that comes with protection from cancer can not be quantified.

It is hoped, especially for developing countries, that the vaccinations can be eventually given in one dose or through oral administration. Lack of access to medical care is a problem in many areas of the world; the observation that 80% of women with cervical cancer are in developing countries clearly illustrates this fact (Hanna et al., Roden et al.). Even in the US many people are forced to go without medical insurance at some point in their lives. HPV vaccination, especially in childhood when other vaccinations are needed, could eventually lead to the elimination of cervical cancer. While this is not as inexpensive or easy as a glass of water a day, a half a million women a year could avoid the pain of cervical cancer.

American Cancer Society, Vol. 57, No. 1, 1/2007

Hanna, E. and G. Bachman. HPV vaccination with Gardasil a breakthrough in women’s health. Informa Healthcare, 2006.

Calloway, C. et al. A Content Analysis of News Coverage of the HPV Vaccine by US Newspapers, January 2002-June 2005. Journal of Women’s Health. Vol. 15 No. 7, 2006.

Dunne, E. et al. Prevalence of HPV Infection among Men: A Systematic Review of the Literature. The Journal of Infectious Diseases. Vol. 194, p1044-1057, 2006.

Hymel, P. A. Decreasing Risk: Impact of HPV Vaccination on Outcomes. The American Journal of Managed Care. Vol. 12, No. 17.

Roden, R. and T.C. Wu. How will HPV vaccines affect cervical cancer? Nature Reviews. Vol. 6, 2006.