January is Cervical Cancer Awareness Month, which gives us an opportunity to learn about the virus that causes most cancers of the cervix (as well as other cancers). More than six million Americans are infected with human papillomavirus (HPV) every year, making it one of the most common sexually transmitted infections. There are more than 100 different strains of the virus, some of which can cause genital warts and others of which can lead to cancer. In most cases, an HPV infection will clear up within eight to 13 months, but it can lurk undetected for years, which makes cancer screening very important for anyone who has been sexually active.
Most sexual activities – especially those involving genital-to-genital contact, i.e., vaginal and anal intercourse or simply rubbing genitals together, but also those involving oral and manual contact – can transmit HPV. Although HPV is best known for its connection to cervical cancer in women, it can affect either sex and cause cancers of the vulva, vagina, cervix, penis, anus, oral cavity, or pharynx.
Together, HPV-16 and HPV-18 cause about 70 percent of cervical cancers. Fifty percent of U.S. women who die of cervical cancer have never had a Pap smear; in countries without widespread access to Pap smears, cervical cancer remains a major cause of death.
A person carrying HPV can transfer the virus to a sexual partner through skin-to-skin contact, probably through microscopic tears in the skin. The virus injects its DNA into the human cell, where the host’s machinery makes copies of the virus. If the infection becomes chronic, the viral DNA and host cells’ DNA combine, which leads to the production of proteins coded by the virus. While our immune systems are usually able to regulate cell division to protect against uncontrolled growth, a protein from a high-risk strain of HPV can interfere with this process, which increases the risk for tumor growth.
The search for a vaccine began in the 1980s, when HPV was confirmed as the cause of cervical cancer. In 2006, the FDA approved Gardasil and Cervarix, both of which inoculate against HPV infection. Because HPV is so easily spread and can have potentially fatal consequences, the vaccine can play a huge role in cancer prevention alongside normal screening methods. Both vaccines protect against cancer-causing HPV-16 and HPV-18. Additionally, Gardasil protects against two wart-causing strains of HPV: HPV-6 and HPV-11.
Gardasil is produced with a yeast, Saccharomyces cerevisiae, that has been genetically modified to produce only the virus’ outer protein shell. In a normal HPV infection, the virus will commandeer a skin cell, which is directed by the viral DNA to manufacture copies of the virus. The vaccine, on the other hand, does not contain viral DNA, protecting the recipient from infection. The yeast-produced proteins self-assemble into a perfect replica of the HPV outer shell. The vaccine is composed of the virus-like particles, an adjuvant, and a buffer, all of which are suspended in a sterile liquid. The antibodies a vaccine recipient produces in response to the impostor viral proteins protect him or her from future infection by the actual virus. The body can now recognize the outer shell of HPV and stimulate an immune response to it upon subsequent exposure.
The HPV vaccine is approved for anyone between the ages of 9 and 26. Because cervical cancer is the most common cancer associated with the virus, the vaccine is generally marketed toward girls, but there are reasons to administer it to boys as well. Though not as common, HPV can lead to cancer in males. At the very least, a male can pass the virus to his sexual partner(s), putting them at risk. Additionally, Gardasil protects both males and females against the most common types of genital warts. Widespread vaccination, regardless of sex, reduces the prevalence of the virus in the general population, which benefits everyone.
In the United States, controversy has surrounded the introduction of the HPV vaccine. On one side, there are religious objections related to the sexual aspect of the disease, and on another side, there is a distrust of vaccines among a significant minority of people. In 2008, 37 percent of girls, ages 13 to 17, initiated the HPV vaccination process, and only half of this group completed it.
Many Planned Parenthood health centers, as well as other clinics and health-care providers, offer the HPV vaccine. More information about HPV and the vaccine is available on the websites for Planned Parenthood and the Centers for Disease Control.