An investigational vaccine against four types of human papillomavirus effectively prevented cancerous and precancerous changes in the cervix, according to results that will be presented today at the annual meeting of the Infectious Diseases Society of America (IDSA).
Human papillomavirus (HPV) is a sexually transmitted infection that is the primary cause of cervical cancer. Different types of HPV are classified as “low-risk” or “high-risk” based on how likely they are to cause cervical cancer. While several types of HPV have been linked with cervical cancer, HPV types 16 and 18 appear to pose the greatest risk. Recent research in the area of cervical cancer has focused on screening women for specific types of HPV and on developing an HPV vaccine to prevent cervical cancer.
Gardasil™ is an investigational vaccine that targets four types of HPV – 6, 11, 16 and 18. Types 6 and 11 are common causes of genital warts, and types 16 and 18 are common causes of cervical cancer.
Researchers conducted a phase III clinical trial of Gardasil among 12,167 women between the ages of 16 and 23 years. Women were enrolled from 13 countries, including the United States. Study participants were randomly assigned to receive either three doses of the vaccine or a placebo. The objective of the study is to assess whether the vaccine reduces the risk of cervical cancer, precancerous changes to the cervix and genital warts.
A presentation at the 2005 annual meeting of the Infectious Diseases Society of America addresses the effect of the vaccine on risk of precancerous changes to the cervix and very early stage cervical cancer. Specifically, it assessed the risk of cervical intraepithelial neoplasia (CIN) types 2 and 3 and adenocarcinoma in situ (AIS). These are thought to be precursors to invasive cervical cancer.
After two-years of follow-up, researchers report:
o Vaccination with Gardasil prevented HPV 16- and 18-associated CIN 2 and 3, as well as AIS.
o One case occurred among women assigned to the vaccine group, compared to 36 cases among women assigned to the placebo group.
o The most common adverse effect of vaccination was discomfort at the injection site.
The researchers conclude that Gardasil effectively prevents HPV 16- and 18- associated precancerous cervical changes and very early stage cervical cancer. Additional follow-up is necessary to confirm that the vaccine will prevent invasive cervical cancers. Subsequent analyses will also assess whether the vaccine prevents genital warts.
Reference: Skjeldestad FE. Prophylactic quadrivalent human papillomavirus (HPV) (Types 6, 11, 16, 18) L1 virus-like particle (VLP) vaccine (Gardasil™) reduces cervical intraepithelial neoplasia (CIN) 2/3 risk. Abstract LB-8a. Presented at the 2005 meeting of the Infectious Diseases Society of America.