A Vaccine for Cervical Cancer

The U. S. Food and Drug Administration has approved a vaccine that offers protection against cervical cancer. It works by preventing infection by four strains of the human papillomavirus, HPV, the most prevalent sexually transmitted disease. Gardasil, manufactured by Merck and Co., is the first vaccine designed to prevent a cancer.

Studies show virtually all cases of cervical cancer are cause by HPV. It is transmitted sexually and most of the time human immune systems can get rid of it. However, in the United States alone, about 10,000 new cases of cervical cancer are diagnosed annually and nearly 4,000 women die of cervical cancer each year. The significance of the cervical cancer vaccine in the United States will be enormous. Worldwide, the impact will be even greater. According to the World Health Organization, there were 470,000 new cases of cervical cancer and 233,000 deaths in 2005. It is the second most common cancer in women. It is estimated that the vaccine could lead to a 70% reduction in the incidence of cervical cancer.

There are more than 70 different types of HPV. The vaccine protects against the two types of HPV responsible for 70% of cervical cancer cases. In clinical trials conducted on 21,000 women in the United States and Western Europe it prevented 100 % of cervical cancer related to these two HPV strains in women who had not been previously infected. The vaccine also blocks infection by two other strains responsible for 90% of genital wart cases.

The FDA approved the vaccine for girls between 9 and 26. It was not tested in women older than 26. The recommended age to receive the vaccine will probably be 9 to 12 years old. The vaccine works best when given to girls before they begin having sex and are at risk for contracting HPV infections. The vaccine does not protect against existing HPV infections but will protect against future infections. In women already infected with HPV it could increase their risk of the kind of lesions that can lead to cervical cancer. The vaccine does not eliminate the need for regular screening.

Gardasil is administered by injection of three doses during a six-month period. The second dose is given two months after the first dose; the third is given six months after the first dose. During clinical trials, researchers observed that the antibody levels in women continued to increase with each dose of the vaccine and it is not clear what antibody levels give adequate protection from HPV. It was felt that it would be better to start with high antibody levels to get the greatest HPV protection for the longest time.

Merck estimates that the series of three shots will cost between $300 and $500. It is expected that insurance companies in the U.S. will probably cover the expense of vaccination for girls and women in the recommended age groups.
If the national Advisory Committee on Immunization Practices endorses routine vaccination with Gardasil, it will become a standard of care. Then individual states can decide whether to add the vaccine to the list of others required before students may attend public schools.

Another cervical cancer vaccine, Cervarix, is currently being considered for approval in Canada and Western Europe. It protects against the same HPV types as Gardasil.

For more information on the vaccine and on cervical cancer:
Food and Drug Administration sites:
http://www.fda.gov/bbs/topics/NEWS/2006/NEW01385.html
http://www.fda.gov/womens/getthefacts/hpv.html
Mayo Clinic:
http://www.mayoclinic.com
American Cancer Society:
http://www.cancer.org

Information on HPV:
National Cancer Institute:
http://www.cancer.gov/cancertopics/factsheet/Risk/HPV