What we know
There are as many as 100 strains of HPV, 13 of them considered "high risk" for the development of cervical cancer and its precursors. The vaccine offers protection against four: subtypes 16 and 18, which are responsible for 70 percent of cervical cancers, and subtypes 6 and 11, which cause 90 percent of genital warts and can affect both sexes.
"Cervical cancer is the second leading cause of cancer death in women worldwide," explains Ross Berkowitz, MD, director of Gynecologic Oncology Services at Brigham and Women's Hospital and Dana-Farber. "The vaccine may be used to lower mortality rates, especially in countries or areas with limited access to care. Due to a lack of resources in many countries in the world, patients have no access to Pap smears and, therefore, little opportunity for early detection of cervical cancer."
According to the U.S. Centers for Disease Control and Prevention, at least 50 percent of sexually active people will become infected with HPV at some time in their lives, and every year in the U.S. an estimated 6.2 million people contract the virus. Both men and women can catch it and pass the virus on to their partners without ever knowing it.
HPV lives in the cells of the lower genital tract and is easily contracted through genital-to-genital, hand-to-skin/genital, or mouth-to-genital contact. While using condoms is recommended, it is unclear how much they help, since uncovered areas can still be exposed to the virus. The appropriate use of condoms, however, may reduce the risk of genital warts and other sexually transmitted diseases, and some studies show lower incidence of cervical cancer when they are used.
"Since the 1930s, rates of cervical cancer in the U.S. have declined 70 percent, thanks to early detection through Pap tests and appropriate follow-up with a physician," explains Dr. Feldman. "The vaccine can prevent the spread of HPV, but it's not a cure-all. Women need to have Pap smears within three years of the onset of sexual activity or beginning at age 21. They should continue them annually until age 30, at which point some patients may be able to lengthen the interval to every two to three years."
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