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Human papillomavirus vaccine research focuses on the prevention of cervical cancer. A successful vaccine will especially impact in developing countries, where regular cervical examinations are uncommon. HPV infection is the overwhelming cause of cervical cancer growth in women. 270,000 women died of cervical cancer worldwide in 2002.Cohen J. 2005. High Hopes and Dilemmas for a Cervical Cancer Vaccine. Science, 308(5722): 618-621. According to the American Cancer Society, 3,700 of those deaths occurred in the United States.How Many Women Get Cancer of the Cervix?, American Cancer Society, accessed May 19, 2006 This low figure is credited to the prevalence of regular exams, including pap tests and HPV tests, in the U.S.HPV test: Cervical Cancer QA, accessed May 19, 2006
The vaccines being studied have proven very effective (100% in some studies, referenced below) at stopping HPV, with few or no side effects. Cohen notes that researchers are very optimistic that these vaccines will be available for distribution soon. In May 2006, a Food and Drug Administration advisory panel unanimously approved adoption of the first vaccineFDA Panel Endorses Cervical Cancer Vaccine, AP, accessed May 19, 2006 ; on June 8, 2006, the FDA fully approved the vaccineFDA approves cervical cancer vaccine, AP, accessed June 8, 2006 , to be marketed by Merck as Gardasil, for use in girls and women ages 9 to 26. One property of the vaccines now being researched is their longevity. The most current data indicates that vaccination with a bivalent HPV16/18 vaccine elicits antibody responses that are detectable over 4.5 years after the initial vaccinationLancet 367, April 15, 2006, p 1247-55.
Of the HPV strains that cause cancer, the vaccines currently under examination target only two strains, strains 16 and 18, which account for about 70% of HPV-related cancer cases. Adding other virus types increases cost, complexity and development time, with approximately 13 other virus types required to achieve 100% coverage of cancer-causing strains. Strains 6 and 11, targeted by Merck's vaccine (in addition to 16 and 18), are not responsible for cervical cancer, but rather for genital warts. "Warts cause considerable discomfort and psycho-social trauma, so this makes the vaccine more attractive and also provides a reason other than altruism for men to be immunized," explains John Schiller of the National Cancer Institute HPV vaccine moves into late stage trials, Nature Medicine 7, 388 (2001), accessed May 19, 2006.
Vaccines and clinical trials
Studies testing the clinical efficacy of a human papillomavirus vaccine are currently underway worldwide. Two vaccines target the virus strains of human papillomavirus that are most often responsible for cervical cancer and genital warts. Using techniques developed by scientists at several government and academic laboratories (for the history of the development of the VLP technology see: Who Invented the VLP Cervical Cancer Vaccines? McNeil, C., Journal of the National Cancer Institute, 2006, 98(7): 433.), two companies, Merck & Co. and GlaxoSmithKline (GSK) have developed and commercialized HPV vaccines. Merck's vaccine, Gardasil, is a quadrivalent vaccine that targets strains 6, 11, 16 and 18 of the virus. As of May 2006, Gardasil has completed the final stages of a Phase III human trial, including over 25,000 women Development of new vaccines, World Health Organization, accessed May 19, 2006. In May 2006 the Food and Drug Administration advisory panel unanimously endorsed the vaccine for use in women aged 9-26. FDA approved Gardasil in June 2006. Merck intends to release the vaccine commercially before the end of the year. It is expected that the vaccine will cost approximately US$300-$500. GSK is also working on a vaccine, Cervarix, which targets only the cancer-causing strains 16 and 18. GSK's vaccine is also in the midst of a Phase III human trial (with over 30,000 women); that study commenced in 2004 and is still running. Early results have indicated that HPV vaccines are extremely effective. For example, results of a phase III trial (at 48 months) of an HPV16 vaccine demonstrated that the vaccine is 100% effective at preventing cervical intraepithelial neoplasia Efficacy of Human Papillomavirus-16 Vaccine to Prevent Cervical Intraepithelial Neoplasia, Obstetrics & Gynecology 2006;107:18-27.
It is important to note that women already infected with the HPV virus will not benefit from the HPV vaccine and are at risk of developing cervical cancer within 15-25 years of infection. There are currently no approved therapeutic vaccines against cervical cancer. However, numerous academic laboratories and companies are in the process of developing therapeutic vaccine approaches.
Controversy
Debate has arisen about how vaccination should be implemented if and when the vaccine is approved for use. Due to high incidence and the highly contagious nature of HPV infections, some doctors have advocated vaccination of teenage girls at puberty. Some religious groups oppose mandatory early vaccination, because the vaccine protects against a sexually transmitted disease, citing fears that it could send a subtle message condoning sexual activity before marriage. "I've talked to some who have said, 'This is going to sabotage our abstinence message,'" said Gene Rudd, associate executive director of the Christian Medical and Dental Associations. Epidemiologist Laura Koutsky objects to the idea that the vaccine could be interpreted as giving a green light for girls to have sex: "Why don't you think of this as a red light for cancer?" she responds . Some advocates have taken to calling the vaccine a cervical cancer vaccine.
In Australia, the conservative Liberal Prime Minister John Howard has expressed support for the vaccine's introduction. Other Coalition MPs, most notably Barnaby Joyce, have expressed reluctance to leave approval to the country's Therapeutic Goods Administration, on the grounds that the TGA "will talk about the therapeutic aspects — they are not there to talk about the psychological implications or the social implications". The HPV vaccine debate coincides with another debate on the federal government's role in drug approval; since late 2005, abortion rights factions have moved to wrest authorisation of the abortion pill RU486 from the Australian health minister's control to the TGA.
Dr. Reginald Finger is a member of the Advisory Committee on Immunization Practices, an influential government committee charged with advising the U.S. President on prevention of vaccine-related diseases. He has said that marketing the HPV vaccine as a medicine that makes adolescent sex safer would be harmful to an abstinence-only message. He has also said that an HIV vaccine's effects on sexual activity would have to be carefully considered. However, in the public session of the recent FDA advisory meeting there were no public objections to the implementation of the vaccine.
The vast majority of cervical cancer deaths occur in developing countries; however, the vaccine's penetration is expected to be limited there by the anticipated cost of US$300-500 and the necessity of a three-shot immunization schedule.
Merck has responded to the vaccine cost issue by announcing a vaccine patient assistance program, providing free HPV vaccineHPV/Cervical cancer vaccine approved 6/8/2006, Merck announces vaccine patient assistance programPress release, June 8, 2006 to patients who cannot otherwise afford it.
References
External links
- Defusing the War Over the "Promiscuity" Vaccine, TIME Magazine, june 21, 2006
"HPV vaccine"