Related Pages Search for Clinical Trials 1 NCI's PDQ® Cancer Clinical Trials Registry. HPV Vaccines for Cervical Cancer 2 A collection of material about HPV and vaccines designed to prevent infections from certain types of the virus that may lead to cervical cancer. Cervical Cancer Home Page 3 NCI's gateway for information about cervical cancer.

Adapted from the NCI Cancer Bulletin, vol. 4/no. 24, August 21, 2007 (see the current issue ⁴).

A vaccine developed to prevent infection with human papillomaviruses (HPV), the cause of cervical cancer, was found to be ineffective for treating women with pre-existing HPV infections, according to a study published in the August 15, 2007, Journal of the American Medical Association (see the journal abstract ⁵).

The study, a community-based, randomized trial of 2,189 women in Costa Rica, was conducted by National Cancer Institute's Division of Cancer Epidemiology and Genetics (DCEG) and Costa Rican investigators (see the protocol summary ⁶). The researchers found no significant difference in how quickly an HPV infection was cleared among those who received the HPV vaccine compared with the control group who received vaccinations for hepatitis A.

At the six-month follow-up visit, rates of viral clearance were 33.4 percent for women who received vaccines against HPV types 16 and 18 compared with a 31.6 percent rate among the control group. At the 12-month visit, rates of clearance in the HPV vaccine group were 48.8 percent versus 49.8 percent for the controls.

"The main finding of the study was to demonstrate that among women who are already infected, the HPV vaccine does not help accelerate the rate of viral clearance," commented Dr. Allan Hildesheim with DCEG. "Therefore, women who are infected with HPV should not take the vaccine to treat their infections or associated lesions."

The study reinforces the importance of targeting HPV vaccination towards adolescent girls before they begin sexual activity "because that would maximize the benefit provided by vaccination," he added.

The study is part of a larger community-based clinical trial of 7,466 Costa Rican women ⁷. The larger study will address broad issues about the vaccine including efficacy, duration of protection, and global impact of vaccination on HPV and HPV-related disease. Among other questions, "the study will address whether vaccination is important for women who have previously been infected and have cleared the infection by themselves," said Dr. Hildesheim.

Glossary Terms

In a clinical trial, the group that does not receive the new treatment being studied. This group is compared to the group that receives the new treatment, to see if the new treatment works.

Effectiveness. In medicine, the ability of an intervention (for example, a drug or surgery) to produce the desired beneficial effect.

A type of virus that can cause abnormal tissue growth (for example, warts) and other changes to cells. Infection for a long time with certain types of HPV can cause cervical cancer. HPV can also play a role in some other types of cancer, such as anal, vaginal, vulvar, penile, and oropharyngeal cancers. Also called human papillomavirus.

An area of abnormal tissue. A lesion may be benign (not cancer) or malignant (cancer).

A study in which the participants are assigned by chance to separate groups that compare different treatments; neither the researchers nor the participants can choose which group. Using chance to assign people to groups means that the groups will be similar and that the treatments they receive can be compared objectively. At the time of the trial, it is not known which treatment is best. It is the patient's choice to be in a randomized trial.

In statistics, describes a mathematical measure of difference between groups. The difference is said to be significant if it is greater than what might be expected to happen by chance alone. Also called statistically significant.

A substance or group of substances meant to cause the immune system to respond to a tumor or to microorganisms, such as bacteria or viruses. A vaccine can help the body recognize and destroy cancer cells or microorganisms.