Preventing Virus-Associated Cancers
More than 2 million cancers worldwide each year are caused by 10 different infectious agents. Seven of these agents are viruses, including the human papillomavirus (HPV, of which there are 13 high-risk types), the hepatitis B virus (HBV), the hepatitis C virus (HCV), and the Epstein-Barr virus (EBV).
The HPV vaccines that are currently available are highly effective in preventing the development of high-grade cervical lesions, which are precursors to cervical cancer that are caused by persistent infections with high-risk HPV types. Because the same HPV types (16 and 18) that cause about 70% of all cervical cancers also cause most cases of vaginal, vulvar, anal, penile, and oropharyngeal cancers, immunization may reduce the incidence of these cancers as well.
Despite the ready availability of HPV vaccines in the United States, vaccination rates remain low. These low vaccination rates stand in sharp contrast with the vaccination rate for another cancer prevention vaccine, the HBV vaccine. HBV is a major cause of liver cancer, and vaccination against this virus is nearly universal in this country.
Additional NCI-funded research will build on efforts against HPV-associated cancers and focus on other cancers that have viral causes.
Broaden the Prevention of HPV-Associated Cancers
NCI efforts against HPV-associated cancers include the following:
- NCI is sponsoring a clinical trial to assess the efficacy of immunization with one dose of HPV vaccine. This research builds on previous NCI-led research that showed that two doses of HPV vaccine were as effective as three doses, a finding that changed national vaccine guidelines for younger adolescents. The finding that two doses is sufficient for this group is important because administering fewer doses is logistically simpler and more cost effective, which is especially important in resource-poor areas. One dose would further reduce costs and improve vaccine uptake, thereby having a greater impact on preventing cervical and, possibly, several other types of cancer.
- HPV vaccines work best when given before a person is exposed to the virus. For women already exposed and at risk of cervical cancer, NCI-supported researchers are trying to develop vaccines against virus antigens associated with HPV-induced cancers. These antigens include the HPV proteins E6 and E7. Vaccines targeting these antigens may prevent high-risk precancerous growths from progressing to cervical cancer.
Develop New Prevention Methods against Additional Cancer-Causing Viruses
The successful production of vaccines against additional viruses that cause cancer will have tremendous global impact. For example, Epstein-Barr virus (EBV) infections cause an estimated 200,000 new cases of cancer each year worldwide. Vaccines against EBV, which causes Burkitt lymphoma, some types of Hodgkin and non-Hodgkin lymphoma, and about 10% of gastric (stomach) cancers, are in development. NCI also supports research that is essential to understanding how EBV interacts with other risk factors to drive cancer development and to find other ways to intervene to prevent EBV-associated cancers.
- NCI is supporting research to broaden the use of currently available vaccines against cancer-causing viruses.
- NCI is also supporting research to develop additional vaccines against the currently targeted viruses and other cancer-causing viruses.
- The ultimate goal of this research is to prevent cancer caused by viruses.