|Target disease||human papillomavirus (Types 16, 18, 6, and 11)|
|Pregnancy cat.||B (US)|
|Legal status||℞-only (US)|
| (what is this?)
Gardasil (Merck & Co.), also known as Gardisil or Silgard, is a vaccine for use in the prevention of certain types of human papillomavirus (HPV), specifically HPV types 6, 11, 16 and 18. HPV types 16 and 18 cause an estimated 70% of cervical cancers, and are responsible for most HPV-induced anal, vulvar, vaginal, and penile cancer cases. HPV types 6 and 11 cause an estimated 90% of genital warts cases. Though it does not treat existing infection, vaccination is still recommended for HPV positive individuals, as it may protect against one or more different strains of the disease. The HPV strains that Gardasil protects against are sexually transmitted. It was approved in the US on June 8, 2006 by the U.S. Food and Drug Administration (FDA). The FDA recommends vaccination before adolescence and potential sexual activity.
The research that led to the development of the vaccine began in the 1980s by groups at the University of Rochester, Georgetown University, and the US National Cancer Institute (NCI). In 1991, Australian investigators Jian Zhou and Ian Frazer at The University of Queensland found a way to form non-infectious virus-like particles (VLP), which could also strongly activate the immune system. However, these VLPs assembled poorly and did not have the same structure as infectious HPV. In 1993, a laboratory at the US National Cancer Institute was able to generate HPV16 VLPs that were morphologically correct. These VLPs were the basis for the HPV16 component of the Gardasil vaccine. Upon commercialization of the vaccine, disputes involving intellectual property ownership arose between the various groups that had played a role in its development.
Merck & Co. conducted a Phase III study named Females United to Unilaterally Reduce Endo/Ectocervical Disease (FUTURE II). This clinical trial was a randomized double-blind study with one controlled placebo group and one vaccination group. Over 12,000 women aged 16–26 from thirteen countries participated in the study. Each woman was injected with either Gardasil or a placebo on day 1, month 2, and month 6. In total, 6,082 women were given Gardasil and 6,075 received the placebo. Subjects in the vaccine group had a significantly lower occurrence of high-grade cervical intraepithelial neoplasia related to HPV-16 or HPV-18 than did those in the placebo group. On February 27, 2006, the independent Data and Safety Monitoring Board recommended the clinical trials be terminated on ethical grounds, so that young women on placebo could receive Gardasil. Merck tested the vaccine in several hundred 11- and 12-year-old girls.
Indications and prevalence
Gardasil is a prophylactic HPV vaccine, meaning that it is designed to prevent HPV infections. For maximum effect, it is recommended that girls receive the vaccine prior to becoming sexually active. However, women who were already infected with one or more of the four HPV types targeted by the vaccine (6, 11, 16, or 18) were protected from clinical disease caused by the remaining HPV types in the vaccine.
Since Gardasil will not block infection with all of the HPV types that can cause cervical cancer, the vaccine should not be considered a substitute for routine pap smears.
Fewer HPV infections mean fewer complications from the virus and less time and money spent on the detection, work-up, and treatment of cervical cancer and its precursor, cervical dysplasia. It prevents infertility caused by cervical biopsies and reduces the severe respiratory problems of children who are infected by HPV from their mothers.
In addition, protection against HPV 6 and HPV 11 is expected to eliminate 90% of the cases of genital warts. Gardasil also protects against vulvar and vaginal cancers caused by HPV types 16 and 18.
In December 2010, Gardasil was approved by the FDA for prevention of anal cancer and associated precancerous lesions due to human papillomavirus (HPV) types 6, 11, 16, and 18 in people ages 9 through 26 years.
HPV infections, especially HPV 16, contribute to some head and neck cancer (HPV is found in an estimated 26-35% of head and neck squamous cell carcinoma). In principle, HPV vaccines may help reduce incidence of such cancers caused by HPV, but this has not been demonstrated.
Merck was denied FDA approval to market Gardasil to women aged 27 to 45. Although it was found to be safe and effective in the prevention of genital warts, it was not effective in the prevention of cervical cancer in that age group.
Use in males
Gardasil is also effective in males, providing protection against genital warts, anal cancer, and some potentially precancerous lesions caused by some HPV types. An ongoing study of 4,065 males demonstrated the efficacy of Gardasil in males who did not have HPV infection prior to vaccination. The vaccination is expected to protect against penile cancer and anal cancer caused by included HPV types, and research in this area is ongoing. Gardasil vaccine has been shown to significantly decrease the risk of young men contracting genital warts. In the United States the U.S. Food and Drug Administration (FDA) approved administration of the vaccine to males between ages 9 and 26 in October 2009. In the UK, HPV vaccines are licensed for males aged 9 to 15 and for females aged 9 to 26.
Men who have sex with men (MSM) are particularly at risk for conditions associated with HPV types 6, 11, 16, and 18; diseases and cancers that have a higher incidence among MSM include anal intraepithelial neoplasias, anal cancers, and genital warts. Type 16 is also associated with oropharyngeal squamous-cell carcinoma, a form of throat cancer. A 2005 study in San Francisco found that 95% of HIV-infected gay men also had anal HPV infection, of which 50% had precancerous HPV-caused lesions.
Gardasil is given in three 0.5 milliliter injections over six months. The second injection is two months after the first, and the third injection is four months after the second shot was administered.
- Major capsid protein L1 of HPV types 6, 11, 16, and 18
- amorphous aluminum hydroxyphosphate sulfate (adjuvant)
- yeast protein
- sodium chloride
- polysorbate 80
- sodium borate
The HPV major capsid protein, L1, can spontaneously self-assemble into virus-like particles (VLPs) that resemble authentic HPV virions. Gardasil contains recombinant VLPs assembled from the L1 proteins of HPV types 6, 11, 16 and 18. Since VLPs lack the viral DNA, they cannot induce cancer. They do, however, trigger an antibody response that protects vaccine recipients from becoming infected with the HPV types represented in the vaccine. The L1 proteins are produced by separate fermentations in recombinant Saccharomyces cerevisiae and self-assembled into VLPs.
The National Cancer Institute says, "Studies have shown that both Gardasil and Cervarix prevent nearly 100 percent of the precancerous cervical cell changes caused by the types of HPV targeted by the vaccine for up to 4 years after vaccination among women who were not infected at the time of vaccination."
Gardasil has been shown to be partially effective (approximately 38%) in preventing cervical cancer caused by ten other high-risk HPV types.
Antibody levels at month 3 (1 month postdose 2) are substantially higher than at month 24 (18 months postdose 3), suggesting that protection is achieved by month 3 and perhaps earlier. This does not imply that the third dose can be skipped. One study has shown that Cervarix may be effective with fewer than three doses, but the result may not apply to Gardasil and further study is needed.
As of February 2009[update], 40 million doses of Gardasil had been distributed worldwide. The vaccine was tested in thousands of females (ages 9 to 26). The Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) consider the vaccine to be safe. It does not contain mercury, thiomersal, live viruses or dead viruses, only virus-like particles, which cannot reproduce in the human body.
The FDA and the CDC say that the vaccine has only minor side effects, such as soreness around the injection area. Fainting is more common among adolescents receiving the Gardasil vaccine than in other kinds of vaccinations. Patients should remain seated for 15 minutes after they receive the HPV vaccine. There have been reports that the shot is more painful than other common vaccines, and the manufacturer Merck partly attributes this to the virus-like particles within the vaccine. General side effects of the shot may include joint and muscle pain, fatigue, physical weakness and general malaise.
An update on adverse events was published by the Journal of the American Medical Association and looked at data from the Vaccine Adverse Event Reporting System (VAERS), covering 12,424 reported adverse events after about 23 million doses of vaccine between June 2006 and December 2008. Most adverse effects were minor and not greater than background rates compared with other vaccines, the exception being higher rates for syncope and venous thromboembolic events. Venous thromboembolic events were noted in 56 reports at a rate of 0.2 cases per 100,000 doses distributed and included 19 cases of pulmonary embolism, four of which were fatal. Overall, 772 events (6.2% of the total number of adverse events, but only 0.003% of the total number of doses) were described as serious and included 32 reported deaths (1 per 1,000,000 doses).
Other adverse events include local site reactions (7.5 cases per 100,000 doses distributed), headaches (4.1 cases per 100,000 doses distributed), hypersensitivity reactions (3.1 cases per 100,000 doses distributed), and urticaria (hives) (2.6 cases per 100,000 doses distributed). A Kaiser Permanente study tracking 190,000 girls and women post-vaccination for two years found that rates of the autoimmune disorders lupus, rheumatoid arthritis, juvenile rheumatoid arthritis, idiopathic thrombocytopenic purpura (ITP), hemolytic anemia, multiple sclerosis, thyroiditis and type 1 diabetes mellitus in vaccinated populations were the same as in unvaccinated populations.
The FDA and the CDC said that with millions of vaccinations "by chance alone some serious adverse effects and deaths" will occur in the time period following vaccination, but have nothing to do with the vaccine. More than 20 women who received the Gardasil vaccine have died, but these deaths have not been causally connected to the shot. Where information has been available, the cause of death was explained by other factors. Likewise, a small number of cases of Guillain-Barré Syndrome (GBS) have been reported following vaccination with Gardasil, though there is no evidence linking GBS to the vaccine. It is unknown why a person contracts GBS, or what initiates the disease.
The FDA and the CDC monitor events to see if there are patterns, or more serious events than would be expected from chance alone. The majority (68%) of side effects data were reported by the manufacturer, but in about 90% of the manufacturer reported events, no follow-up information was given that would be useful to investigate the event further. In February 2009, the Spanish ministry of health suspended use of one batch of Gardasil after health authorities in the Valencia region reported that two girls had become ill after receiving the injection. Merck has stated that there was no evidence Gardasil was responsible for the two illnesses.
Public health advantages
The National Cancer Institute writes:
- Widespread vaccination has the potential to reduce cervical cancer deaths around the world by as much as two-thirds, if all women were to take the vaccine and if protection turns out to be long-term. In addition, the vaccines can reduce the need for medical care, biopsies, and invasive procedures associated with the follow-up from abnormal Pap tests, thus helping to reduce health care costs and anxieties related to abnormal Pap tests and follow-up procedures.
Long-term impact and cost-effectiveness
|This article is outdated. (July 2009)|
One unknown property of the vaccines now being researched is the persistence of their protective effects. Since the Gardasil vaccine has been administered for only a few years now, it is unknown whether it will provide lifelong immunity to recipients. In coming decades, further study will answer this question.
Whether the effects are temporary or lifelong, widespread vaccination could have a substantial public health impact. 270,000 women died of cervical cancer worldwide in 2002. Acting FDA Administrator Andrew von Eschenbach said the vaccine will have "a dramatic effect" on the health of women around the world. Even in the United States, where screening programs are routine, the National Cancer Institute estimated that 9,700 women would develop cervical cancer in 2006, and 3,700 would die.
Merck and CSL Limited are expected to market Gardasil as a cancer vaccine, rather than an STD vaccine. It remains unclear how widespread the use of the three-shot series will be, in part because of its $525 list price ($175 each for three shots). 
Studies using different pharmacoeconomic models predict that vaccinating young women with Gardasil in combination with screening programs may be more cost effective than screening alone. These results have been important in decisions by many countries to start vaccination programs. For example, the Canadian government approved $300 million to buy the HPV vaccine in 2008 after deciding from studies that the vaccine would be cost-effective especially by immunizing young women. Marc Steben, an investigator for the vaccine, wrote that the financial burden of HPV related cancers on the Canadian people was already $300 million per year in 2005, so the vaccine could reduce this burden and be cost-effective.
Since penile and anal cancers are much less common than cervical cancer, HPV vaccination of young men is likely to be much less cost-effective than for young women.
Diane Harper, one of the lead researchers for Gardasil, has called for more complete warnings for parents and questions its risk-versus-benefit profile because it is not yet known how long the vaccine will be effective once administered. The August 2009 issue of the Journal of the American Medical Association had an article reiterating the safety of Gardasil and another questioning the way it was presented to doctors and parents.
The new vaccine against 4 types of human papillomavirus (HPV), Gardasil, like other immunizations appears to be a cost-effective intervention with the potential to enhance both adolescent health and the quality of their adult lives. However, the messages and the methods by which the vaccine was marketed present important challenges to physician practice and medical professionalism. By making the vaccine's target disease cervical cancer, the sexual transmission of HPV was minimized, the threat of cervical cancer to adolescents was maximized, and the subpopulations most at risk practically ignored. The vaccine manufacturer also provided educational grants to professional medical associations (PMAs) concerned with adolescent and women's health and oncology. The funding encouraged many PMAs to create educational programs and product-specific speakers' bureaus to promote vaccine use. However, much of the material did not address the full complexity of the issues surrounding the vaccine and did not provide balanced recommendations on risks and benefits. As important and appropriate as it is for PMAs to advocate for vaccination as a public good, their recommendations must be consistent with appropriate and cost-effective use.
In an address at the 4th International Public Conference on Vaccination sponsored by the anti-vaccination group the National Vaccine Information Center in October 2009, Diane Harper stated that in countries where Pap smear screening is common, it will take vaccination of a large proportion of women in order to further reduce cervical cancer rates. She also stated that no efficacy trials for children under 15 have been performed.
Political and other controversy
Anti-vaccination and parental groups protested the use of the vaccine after it was revealed the producer of Gardasil, Merck & Co., was lobbying state legislatures to introduce compulsory vaccination against HPV for preteen girls as a requirement for school attendance. Some objections were due to the vaccine protecting against a sexually transmitted disease, human papillomavirus, the primary causative agent of cervical cancer. The vaccine was contrasted to other mandated vaccines that are typically for diseases spread through casual contact, such as measles and mumps. On February 20, 2007, Merck announced its immediate suspension of this campaign, saying, "We're concerned that our role in supporting school requirements is a distraction from that goal (providing women with a vaccine for HPV), and as such have suspended our lobbying efforts."
The governor of Texas, Rick Perry, issued an executive order adding Gardasil to the state's required vaccination list, which was later overturned by the Texas legislature. Perry has also allowed parents to opt out of the program more easily. Through lobbying efforts, Merck has suggested that governments make vaccination with Gardasil mandatory for school attendance, which has upset some conservative groups and libertarian groups. Conservative groups, including the Family Research Council (FRC), have expressed fear that vaccination with Gardasil might give girls a false sense of security regarding sex and lead to promiscuity, but no evidence exists to suggest that girls who were vaccinated later engaged in more sexual activity than unvaccinated girls. Perry's decision was later criticized on September 12, 2011 by fellow presidential candidates Ron Paul and Michele Bachmann during the Republican Party presidential debate as being an overreach of state power in a decision properly left to parents.
In July 2006, the developments by Merck & Co had led to Gardasil being introduced to Canada. The vaccine was developed to prevent the HPV types 6, 11, 16, and 18 from infecting those who are sexually active. The need for the vaccine in Canada was a result of HPV being one of the most frequently occurring sexually transmitted diseases in the country. However, the way the government and pharmaceutical companies went about campaigning the vaccine throughout the country proved to be problematic. As a result of the target audience for the vaccine being females between the ages of 9-26, the Canadian government turned to the school system to administer the vaccine. The Canadian Federal government used $300 million in three years to help administer the vaccine throughout schools. In 2007 the provincial school-based programs used the money to vaccinate school age children. In 2007 debates among the public became prominent as a result of the provincial governments targeting children in grade 8 for the vaccine. The debates became controversial because of the age range used to be immunized and because at the time the vaccine was starting to be used, there was no long-term data provided from clinical trials. Issues also arose from the campaigns used for the vaccine because the young females being vaccinated were not taken into consideration in regards to how they felt about being vaccinated.
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