HPV vaccine

Human papillomavirus (HPV) vaccine is a vaccine that targets certain sexually transmitted strains of human papillomavirus associated with the development of cervical cancer and genital warts.^[1] Two HPV vaccines are currently on the market: Gardasil and Cervarix.^[2]

Of the more than 100 known HPV types, 37 are known to be transmitted through sexual contact. Infection with sexually transmitted HPVs is very common in adult populations worldwide. According to the American Centers for Disease Control, by the age of 50 more than 80% of American women will have contracted at least one strain of HPV.^[3]

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Prevalence of genital HPV

See also: Prevalence of Genital HPV

HPV is highly communicable. A large percentage of the American population is infected with genital HPV.^[4] Because of the infection rate, some American public health experts recommend mandatory HPV vaccination.^[5] Each year, between 250,000 and 1 million American women are diagnosed with cervical dysplasia, which is caused by HPV and is a precursor to cervical cancer.^[6] About 11,000 American women are diagnosed with cervical cancer every year, and about 3,700 die per year of the disease.^[7] Condoms do not provide comprehensive protection against HPV.^[8][9][10] Both men and women are carriers of HPV. To eradicate the disease through vaccine, there will need to be vaccines effective for men.^[11] Studies are being conducted now to determine the efficacy of vaccinating boys with the current vaccine.

There are 19 "high-risk" HPV types can lead to the development of cervical cancer or other genital/anal cancers, and some forms of HPV, particularly type 16, have been found to be associated with a form of throat cancer.^[12] Only a small percentage of women with HPV go on to develop cervical cancer,^[13] nevertheless, most scientific studies have found that human papillomavirus (HPV) infection is responsible for virtually all cases of cervical cancer.^[14][15]

How the vaccine works

The latest generation of preventive HPV vaccines are based on hollow virus-like particles (VLPs) assembled from recombinant HPV coat proteins. The vaccines target the two most common high-risk HPVs, types 16 and 18. Together, these two HPV types currently cause about 70 percent of all cervical cancer. Gardasil also targets HPV types 6 and 11, which together currently cause about 90 percent of all cases of genital warts.^[13]

Gardasil and Cervarix are designed to elicit virus-neutralizing antibody responses that prevent initial infection with the HPV types represented in the vaccine. The vaccines have been shown to offer 100 percent protection against the development of cervical pre-cancers and genital warts caused by the HPV types in the vaccine, with few or no side effects. The protective effects of the vaccine are expected to last a minimum of 4.5 years after the initial vaccination.^[16]

While the study period was not long enough for cervical cancer to develop, the prevention of these cervical precancerous lesions (or dysplasias) is believed highly likely to result in the prevention of those cancers.^[17]

Although a 2006 study suggests that the vaccines may offer limited protection against a few HPV types that are closely related to HPVs 16 and 18, it is clear that other high-risk HPV types can circumvent the vaccines,^[16] and a 2006 study of HPV infection in female university students found that only 14 of 78 infections with high-risk types of HPV were by types 16 and 18, the remaining 64 infections being with 16 other high-risk types of HPV.^[18] Ongoing research is focused on the development of HPV vaccines that will offer protection against a broader range of HPV types. There is also substantial research interest in the development of therapeutic vaccines, which seek to elicit immune responses against established HPV infections and HPV-induced cancers.

Target populations

Gardasil and Cervarix are preventative (rather than therapeutic) vaccines, recommended for women who are 9 to 25 years old and have not contracted HPV. However, since it is unlikely that a woman will have already contracted all four viruses, and because HPV is primarily sexually transmitted, the US Centers for Disease Control and Prevention has recommended vaccination for women as old as 26.

Although HPV types 6 and 11 do not cause cervical cancer, they can cause 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.^[19] From a public health point of view, vaccinating men as well as women is important because it decreases the vaccine pool within the population. HPV also causes anal and penile cancer. In the UK the drug is licensed for girls and boys aged 9 to 15 and for women aged 16 to 26. Thus, the drug has to be administered to adult men "off license".^[20]

When Gardasil was first introduced, it was recommended as a prevention for cervical cancer for women that were 25 years old or younger. New evidence suggests that all Human Papilloma Virus (HPV) vaccines are effective in preventing cervical cancer for women up 45 years of age. "^[21]

Vaccine implementation

In developed countries, the widespread use of good-quality cervical "Pap smear" screening programs has reduced the incidence of invasive cervical cancer, by 50% or more. The current generation of preventive vaccines offers protection against the two HPV types (16 & 18) that currently cause about 70% of cervical cancer cases. Therefore, experts recommend that women combine the benefits of both programs by seeking regular Pap smear screening, even after vaccination.

HPV-induced cervical cancer remains the fifth most common cancer in women worldwide.^[22]

Legislation in the United States

Opt-out policies

Almost all pieces of legislation currently pending in the states that would make the vaccine mandatory for school entrance have an "opt-out" policy.^[23]

Opposition from health insurance companies

There has been significant opposition from health insurance companies to covering the cost of the vaccine ($360).^[24][25][26]

Successful implementations

New Hampshire has adopted a voluntary program, in which it supplies the vaccine free of charge to girls between the ages of 11 and 18. Alaska has adopted a similar voluntary program for girls between the ages of 9 and 18. ^[27] This has met with wide acceptance, with many young women requesting the vaccine. South Dakota and Washington are considering similar measures.^[28]

State-by-State

Other states are also preparing bills to handle issuing the HPV Vaccine.^[29]

Source: National Conference of State Legislatures, state legislatures

History

In work that was initiated in the mid 1980s, the vaccine was developed, in parallel, by researchers at Georgetown University Medical Center, the University of Rochester, the University of Queensland in Australia, and the U.S. National Cancer Institute ^[30] . In 2006, the U.S. Food and Drug Administration approved the first preventive HPV vaccine, marketed by Merck & Co. under the tradename Gardasil. According to Merck press release ^[31], in the second quarter 2007, it had been approved in 80 countries, many under fast-track or expedited review. Early in 2007, GlaxoSmithKline filed for approval in the United States for a similar preventive HPV vaccine, known as Cervarix. In the European Union, GlaxoSmithKline filed the application for approval in March 2006. In June 2007 this vaccine was licenced in Australia.

Opposition

According to the FDA and CDC, the vaccine has only minor side effects, such as soreness around the injection area. The FDA and CDC consider the vaccine to be completely safe. It does not contain mercury, thimerosal or live or dead virus, only virus-like particles, which cannot reproduce in the human body.^[32] Merck, the manufacturer of Gardasil, will continue to test women who have received the vaccine to determine the vaccine's efficacy over the period of a lifetime.

Anti-vaccination groups

A group called the "National Vaccine Information Center" released an article on Feb 22, 2007, about Gardasil. NVIC is a non-governmental, non-profit organization "dedicated to preventing vaccine injuries and deaths through public education." The NVIC does not conduct scientific research, but is highly critical of most vaccinations including the influenza^[33], chickenpox ^[34], tetanus,^[35], and the Measles, Mumps and Rubella (MMR) vaccines.^[36] The NVIC claims "new analysis of the federal Vaccine Adverse Event Reporting System reports of serious health problems following HPV vaccination (Merck's GARDASIL) during the last six months of 2006." However, reports from the Vaccine Adverse Event Reporting System database are subject to interpretation as explained at the official website: "When evaluating data from VAERS, it is important to note that for any reported event, no cause and effect relationship has been established... VAERS collects data on any adverse event following vaccination, be it coincidental or truly caused by a vaccine." [34] The NVIC chooses to interpret the information in VAERS to mean that "two thirds of the 385 adverse incidents which the NVIC says are related to Gardasil injections required secondary medical treatment." The FDA does not believe the vaccine causes serious health problems. The NVIC article goes on to say, "event reports to VAERS do[es] not prove causation." At this time, however, the NVIC chooses to draw a causal relationship between Gardasil and what the FDA believes are unrelated illnesses.

Religious right and conservative groups

In October 2007, the conservative group Judicial Watch reported that the known total numbers of adverse reactions is 3,461 including eleven deaths since FDA approval.^[37] However, an FDA spokesperson stated that these deaths are not related to the vaccine, and occurred independently of vaccination.^[38]

Several other conservative groups in the U.S. have publicly opposed the concept of making HPV vaccination mandatory for pre-adolescent girls, asserting that making the vaccine mandatory is a violation of parental rights. Both the Family Research Council and the group Focus on the Family support widespread (universal) availability of HPV vaccines but oppose mandatory HPV vaccinations for entry to public school.^{[39][40][41][42]}

Response

Many organizations disagree with the assessment that the vaccine would increase sexual activity among teens. Dr. Christine Peterson, director of the University of Virginia's Gynecology Clinic, said "The presence of seat belts in cars doesn't cause people to drive less safely. The presence of a vaccine in a person's body doesn't cause them to engage in risk-taking behavior they would not otherwise engage in." ^[43] All states offer an "opt-out" policy which allows parents to not vaccinate their girls for religious reasons.

Vaccination during pregnancy

In the Gardasil clinical trials, 1,115 pregnant women received the HPV vaccine. Overall, the proportions of pregnancies with an adverse outcome were comparable in subjects who received GARDASIL and subjects who received placebo ^[44]. However, the clinical trials had a relatively small sample size. Currently the vaccine is not recommended for pregnant women.^[1] The long term effects of this vaccine on fertility are not known but no effects are anticipated.

Therapeutic HPV vaccines

In addition to preventive vaccines, such as Gardasil and Cervarix, laboratory research and several human clinical trials are focused on the development of therapeutic HPV vaccines. In general these vaccines focus on the main HPV oncogenes, E6 and E7. Since expression of E6 and E7 is required for promoting the growth of cervical cancer cells (and cells within warts), it is hoped that immune responses against the two oncogenes might eradicate established tumors.^[45]

References

See also

• Human Papilloma Virus
• Cervical dysplasia
• Cervical cancer