Human Papillomavirus (HPV) Vaccines
What are human papillomaviruses (HPVs)?Human papillomaviruses (HPVs) are a group of more than 150 related viruses that may cause warts. Some types of HPV are associated with certain types of cancer. These are called "high-risk," oncogenic, or carcinogenic HPVs.Of the more than 150 types of HPV, more than 40 types can be passed from one person to another through sexual contact. Transmission can occur in the genitals, anal, or oral regions.Most HPV infections occur without any symptoms and go away without any treatment over the course of a few years. However, HPV infections sometimes persist for many years, with or without causing detectable cell abnormalities.
What kinds of cancer are related to HPV infection?Infection with high-risk HPV is the major cause of cervical cancer. Almost all women will have an HPV infection at some point, but very few will develop cervical cancer. The immune system of most women will usually suppress or eliminate HPVs. Only HPV infections that are persistent (do not go away over many years) can lead to cervical cancer.Nearly half a million women develop cervical cancer each year worldwide, and more than a quarter of a million die from it. High-risk HPV types also cause most anal cancers. Infection with high-risk HPV is also known to cause some cancers of the oropharynx, vulva, vagina, and penis.
Can HPV infection be prevented?The surest way to eliminate risk for genital HPV infection is to refrain from any genital contact with another individual. For those who are sexually active, a long-term, mutually monogamous relationship with an uninfected partner is the strategy most likely to prevent HPV infection.However, it is difficult to determine whether a partner who has been sexually active in the past is currently infected. Research has shown that correct and consistent condom use can reduce the transmission of HPV between sexual partners. However, because areas not covered by a condom can be infected by the virus, they are unlikely to provide complete protection against transmission of infection.Two vaccines has be approved to prevent HPV infection: Gardasil® and Cervarix®. Both vaccines are highly effective in preventing infections with HPV types 16 and 18, two high-risk HPVs that cause about 70 percent of cervical and anal cancers. Gardasil also prevents infection with HPV types 6 and 11, which cause 90 percent of genital warts.
What are Gardasil and Cervarix?The Gardasil vaccine is produced by Merck & Co., Inc. It is called a quadrivalent vaccine because it protects against four HPV types: 6, 11, 16, and 18. Gardasil is given through a series of three injections into muscle tissue over a 6-month period.Gardasil is used in females for the prevention of cervical cancer, and some vulvar and vaginal cancers, caused by HPV types 16 and 18, and for use in males and females for the prevention of anal cancer and precancerous anal lesions caused by HPV types 16 and 18. Gardasil is also approved for the prevention of genital warts caused by HPV types 6 and 11. The vaccine is approved for these uses in females and males ages 9 to 26.The Cervarix vaccine is produced by GlaxoSmithKline (GSK). It is called a bivalent vaccine because it targets two HPV types: 16 and 18. This vaccine is also given in three doses over a 6-month period. Cervarix is approved for use in females ages 9 to 25 for the prevention of cervical cancer caused by HPV types 16 and 18.Neither of these HPV vaccines has been proven to provide complete protection against persistent infection with other HPV types, although some initial results suggest that both vaccines might provide partial protection against a few additional HPV types that can cause cervical cancer.Overall, about 30 percent of cervical cancers will not be prevented by these vaccines. Also, in the case of Gardasil, 10 percent of genital warts will not be prevented by the vaccine. Neither vaccine prevents other sexually transmitted diseases, nor do they treat HPV infection or cervical cancer.Because the vaccines do not protect against all HPV infections that cause cervical cancer, it is important for vaccinated women to continue to undergo cervical cancer screening. There could be some future changes in recommendations for vaccinated women.
How do HPV vaccines work?The HPV vaccines work like other immunizations that guard against viral infections. The investigators hypothesized that the unique surface components of HPV might create an antibody response that is capable of protecting the body against infection, and that these components could be used to form the basis of a vaccine.The HPV surface components can interact with one another to form virus-like particles (VLP) that are not infectious, because they lack DNA. However, these VLPs can attach to cells and stimulate the immune system to produce antibodies that can prevent the complete papillomavirus, in future encounters, from infecting cells.Although HPV vaccines can help prevent future HPV infection, they do not help eliminate existing HPV infections.
How effective are the HPV vaccines?Gardasil and Cervarix are highly effective in preventing infection with the types of HPV they target. The vaccines have been shown to provide protection against persistent cervical HPV 16/18 infections for up to 8 years, which is the maximum time of research follow-up thus far. More will be known about the total duration of protection as research continues.HPV vaccination has also been found to prevent nearly 100 percent of the precancerous cervical cell changes that would have been caused by HPV 16/18.A recent analysis of data from a clinical trial of Cervarix found that this vaccine is just as effective at protecting women against persistent HPV 16 and 18 infection in the anus as it is at protecting them from these infections in the cervix.
About STDs (CDC website)
About HPV (CDC website)
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