The HPV Vaccine: Preventing Cancer in Women
- Created on January 15th, 2007
Cervical cancer is the fourth–leading cause of cancer–related deaths among women. The American Cancer Society estimates that in 2006, approximately 9,700 new cases of cervical cancer will be diagnosed and approximately 3,500 women will die from this disease. Although the number of deaths caused by cervical cancer has continued to decline largely due to the Pap smear (a test that detects cervical cancer in its early stages, when treatment is most successful), prevention of the disease is preferable to treatment. It now appears that prevention of cervical cancer is not just a pipe dream, but a medical reality that has the potential to make cervical cancer medical history.
Cervical cancer is caused by the human papilloma virus, known as HPV–the most commonly sexually transmitted viral infection in the US today. Most of the 40 different strains of HPV that infect the lower genital tract (cervix, vagina, vulva, and anus) cause no symptoms at all. However, two types of the virus (HPV 6 and HPV 11) cause genital warts and precancer (called dysplasia) of the genitals. These two types are almost never associated with cancer. Two other types of the virus (HPV 16 & HPV 18) are found in 70 to 80% of all cervical cancers. The viruses are transmitted through unprotected sexual intercourse. Sexually active women who have multiple sex partners or who smoke further increase their risk of developing cervical cancer.
The new vaccine is designed to prevent cervical cancer by stimulating the body’s immune system to make antibodies that will prevent the virus from infecting the woman. Unlike many vaccines that may contain live or killed virus particles, the HPV vaccine does not contain any genetic material responsible for creating warts, dysplasia or cancer. Instead, the HPV virus is made up of the outer protein coat (cover) of the HPV virus. This cover tricks the immune system and causes it to make antibodies that protect the patient from infection. Because the vaccine contains none of the harmful viral genetic material, the vaccine is quite safe to administer to patients.
The FDA recently approved the first commercially available HPV vaccine for use in humans, based on several clinical studies that demonstrate the effectiveness of this preventative vaccine. In those studies, the HPV vaccine was shown to be 90 to 100% effective in preventing the transmission of HPV infection and the development of pre–cancer. Currently, the vaccine is recommended for all girls between the ages of 11 and 12. It is administered as a three–shot series: an initial injection followed by injections one month and six months later. There is evidence that the vaccine may be effective in women up to age 26. Information on vaccinating boys or men is still in review, but appears to be effective.
The results from these studies are exciting. The vaccine appears to be safe, well tolerated, and effective in preventing HPV infection. While the duration of protection from the vaccine still needs further evaluation, HPV vaccines are an important strategy for disease prevention. This major medical advancement is an exciting new complement to patient education, screening with Pap smears and other lifestyle changes in the battle against genital warts, cervical dysplasia, and cervical cancer.