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REPORT TO CONGRESS

Prevention of Genital Human Papillomavirus Infection

Centers for Disease Control and Prevention
Department of Health and Human Services

Julie Louise Gerberding, M.D., M.P.H. Director
Centers for Disease Control and Prevention
January 2004

Executive Summary
Prevention of Genital Human Papillomavirus Infection Executive Summary This report describes key aspects of the epidemiology of genital HPV infection and its transmission, and summarizes the best strategies to prevent infections with genital HPV as well as the HPV-associated diseases of genital warts and cervical cancer.

Genital infection with human papillomavirus (HPV) is very common in sexually active men and women and can sometimes have serious health consequences. About 20 million Americans are currently infected, and about 5.5 million people become newly infected each year. The virus can infect the genital skin and the linings of the vagina, cervix, rectum, and urethra. Most infections cause no clinical problems and go away on their own without treatment. Some infections lead to genital warts in men and women, and abnormal Papanicolaou (Pap) tests in women. Treatments are directed to abnormal cells associated with HPV rather than the virus itself; currently there is no curative treatment for HPV infection.

Of greatest importance, persistent infection with certain types of HPV is a leading cause of cervical cancer. Progression from cervical cancer precursor lesions to invasive cancer is a slow process, estimated to take 10–15 years. Cervical cancer is an uncommon consequence of HPV infection in women, especially if they are screened for cancer regularly with Pap tests and have appropriate follow-up of abnormalities. The purpose of screening with the Pap test is to detect cervical abnormalities that can be treated, thereby preventing progression to invasive cervical cancer, and also to detect invasive cervical cancer at a very early stage. If detected early and managed promptly, survival rates for cervical cancer are over 90%. In the past 40 years, widespread cervical cancer screening using the Pap test and treatment of precancerous cervical abnormalities have resulted in a dramatic decrease in the incidence and mortality due to cervical cancer in the United States. However, each year in the United States, an estimated 12,200 women develop cervical cancer and 4,100 women die from it. Of women in the United States who develop cervical cancer, about half have never had a Pap test.

Because genital HPV infection is most common in men and women who have had multiple sex partners, abstaining from sexual activity (i.e. refraining from any genital contact with another individual) is the surest way to prevent infection. For those who choose to be sexually active, a monogamous relationship with an uninfected partner is the strategy most likely to prevent future genital HPV infections. For those who choose to be sexually active but who are not in a monogamous relationship, reducing the number of sexual partners and choosing a partner less likely to be infected may reduce the risk of genital HPV infection.

All published epidemiologic studies of HPV have methodologic limitations that make the effect of condoms in the prevention of HPV infection unknown. While a few studies on genital HPV and condom use showed a protective effect, most studies on genital HPV infection and condom use did not show a protective effect. Recognizing that the optimal study design to ensure valid measurements can be problematic, it remains important that further research be done to help determine the efficacy of condoms in preventing HPV infection.

Nevertheless, available studies suggest that condoms reduce the risk of the clinically important outcomes of genital warts and cervical cancer. One possible explanation for the protective effect of condoms against warts and cancer is that condom use could reduce the quantity of HPV transmitted or decrease the likelihood of re-exposure, thereby decreasing the chance of developing clinical disease. An alternative explanation is that condom use may reduce exposure to a co-factor for cervical cancer, such as chlamydia or genital herpes, thereby reducing the chance of cervical cancer.

The available scientific evidence is not sufficient to recommend condoms as a primary prevention strategy for the prevention of genital HPV infection. There is evidence that indicates that the use of condoms may reduce the risk of cervical cancer.

Regarding other possible prevention approaches, no data indicate that treatment of clinical lesions or use of microbicides will prevent transmission of infection, although HPV vaccines are likely to become available in the next few years and may become an important prevention tool.

Summary of Strategies to Prevent Genital HPV Infection
Based on currently available science, the following recommendations summarize the strategies most likely to be effective in preventing future infections with genital HPV infection and cervical cancer.

Individual Strategies:

* The surest way to eliminate the risk for future genital HPV infections is to refrain from any genital contact with another individual.

* For those who choose to be sexually active, a long-term, mutually monogamous relationship with an uninfected partner is the strategy most likely to prevent future genital HPV infections. However, it is difficult to determine whether a partner who has been sexually active in the past is currently infected.

* For those choosing to be sexually active and who are not in long-term mutually monogamous relationships, reducing the number of sexual partners and choosing a partner less likely to be infected may reduce the risk of genital HPV infection. Partners less likely to be infected include those who have had no or few prior sex partners.

* While available scientific evidence suggests that the effect of condoms in preventing HPV infection is unknown, condom use has been associated with lower rates of the HPV-associated diseases of genital warts and cervical cancer. The available scientific evidence is not sufficient to recommend condoms as a primary prevention strategy for the prevention of genital HPV infection. There is evidence that indicates that the use of condoms may reduce the risk of cervical cancer.

* Regular cervical cancer screening for all sexually active women and treatment of precancerous lesions remains the key strategy to prevent cervical cancer.

* In the future, receiving a safe and effective HPV vaccine to help prevent genital HPV infection as well as the HPV-associated diseases of genital warts and cervical cancer would be an important prevention measure. However, an effective HPV vaccine would not replace other prevention strategies.

Public Health Strategies
Public health agencies should:

* Promote increased cervical cancer screening among never and rarely-screened women and appropriate follow-up of those with abnormal Pap tests.

* Work with public and private partners to increase awareness about prevention of genital HPV infection and cervical cancer among health care providers and in the general public.

* Collaborate with private industry to promote and accelerate the development of a safe and effective HPV vaccine.

* Continue epidemiologic, laboratory, and behavioral research on genital HPV infection, including studies of the prevalence of HPV in the United States, research on the attitudes and concerns of women diagnosed with HPV infection (e.g., concerns about cancer or about transmission), and surveys of provider knowledge and practices regarding HPV.

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