HPV Vaccine Receives FDA Approval

By Tim Horn, Senior Writer & Editor, AIDSmeds.com

On June 8th, the U.S. Food and Drug Administration (FDA) announced the approval of Gardasil®, the first vaccine developed to prevent cervical cancer, precancerous genital lesions, and genital warts due to human papillomavirus (HPV) types 6, 11, 16 and 18. The vaccine is approved for use in females 9 through 26 years of age.

HPV is the most common sexually transmitted infection in the United States. The U.S. Centers for Disease Control and Prevention (CDC) estimates that approximately 6.2 million Americans become infected with genital HPV each year and that over half of all sexually active men and women become infected at some time in their lives. On average, there are 9,710 new cases of cervical cancer and 3,700 deaths attributed to HPV infection in the United States each year. Worldwide, cervical cancer is the second most common cancer in women; and is estimated to cause over 470,000 new cases and 233,000 deaths each year.

For most women, the body's own defense system will clear the virus and infected women do not develop related health problems. However, some HPV types can cause dysplasia (clusters of abnormal cells) on the lining of the cervix that years later can turn into cancer. Other HPV types can cause genital warts. The vaccine is effective against HPV types 16 and 18, which cause approximately 70% of cervical cancers and against HPV types 6 and 11, which cause approximately 90% of genital warts.

Gardasil, manufactured by Merck & Co., is a recombinant vaccine (contains no live virus) that is given as three injections over a six-month period. Immunization with Gardasil is expected to prevent most cases of cervical cancer due to HPV types included in the vaccine. However, people will not be protected if they have been infected with the HPV type(s) prior to vaccination, indicating the importance of immunization before potential exposure to the virus. Also, Gardasil does not protect against less common HPV types not included in the vaccine, thus routine and regular Pap screening remain critically important to detect precancerous changes to allow treatment before cancer develops.

HPV can also cause dysplasia and cancer of the anus. While anal cancer is rare in the United States, startling numbers come in to play when evaluating the incidence of anal cancer among specific populations. In a 1987 paper published in the New England Journal of Medicine, it was estimated that the incidence of anal cancer among HIV-negative men who engage in receptive anal intercourse with other men was up to 35/100,000 – a rate on a par with the incidence of cervical cancer before routine Pap smears were initiated in the 1940s.

Even more alarming is the incidence rate among HIV-positive men who have sex with men (MSM). During the late 1980s, the incidence of anal cancer among gay men with AIDS was reported to be twice that of men of the same age, race, and sexual orientation in the years before AIDS (1975 to 1979). In other words, the incidence of anal cancer may be greater than 70 of every 100,000 HIV-infected MSM who engage in receptive anal intercourse.

The approval of Gardasil was based on the successful completion of four studies – one in the United States and three multinational – conducted in 21,000 women between the ages of 16 and 26. The results showed that in women who had not already been infected, Gardasil was nearly 100% effective in preventing precancerous cervical lesions, precancerous vaginal and vulvar lesions, and genital warts caused by infection with the HPV types against which the vaccine is directed. While the study period was not long enough for cervical cancer to develop, the prevention of these cervical precancerous lesions is believed highly likely to result in the prevention of those cancers.

The studies also evaluated whether the vaccine can protect women already infected with some HPV types included in the vaccine from developing diseases related to those viruses. The results show that the vaccine is only effective when given prior to infection.

Two studies were also performed to measure the immune response to the vaccine among younger females aged 9 to 15 years. Their immune response was as good as that found in 16 to 26 year olds, indicating that the vaccine should have similar effectiveness when used in the 9 to 15 year age group.

The safety of the vaccine was evaluated in approximately 11,000 individuals. Most adverse experiences in study participants who received Gardasil included mild or moderate local reactions, such as pain or tenderness at the site of injection.

The safety and effectiveness of Gardasil in HIV-positive people have not been determined. Similarly, the effectiveness of Gardasil as a preventive vaccine against cancer and pre-cancerous lesions of the anus, in HIV-negative or HIV-positive men or women, has not been determined.

With the FDA approval of Gardasil, information about the vaccine will also need to be reviewed by the CDC's Advisory Committee on Immunization Practices (ACIP), which will make recommendations regarding the actual use of the vaccine in the United States. Studies indicate that approximately 40% of HPV infections occur within 16 months of first sexual activity. In turn, it is expected that ACIP will recommend Gardasil for school-aged children and young adults who have not yet become sexually active.

Source:

U.S. Food and Drug Administration

 

See this related link:

Human Papillomavirus
(Genital Warts, Cervical Dysplasia & Cancer, Anal Dysplasia & Cancer)

This content is written by the Founder & Writers of AIDSmeds.com, and reviewed by Dr. Howard Grossman, our Medical Editor.
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