The American Cancer Society advocated routine vaccination against human papillomavirus for 11- and 12-year-old girls but cautioned that the potential impact of universal vaccination on cervical cancer rates can only be realized if those underserved populations at greatest risk have access to the vaccine, according to new guidelines released by the Society on Jan. 19.
The guidelines also recommended that girls as young as age 9 years can receive the human papillomavirus (HPV) vaccine and that females 13–18 years old should be vaccinated to catch up on missed vaccine or to complete the number of required injections.
“The vaccine holds remarkable potential, but unless the same populations of women who right now do not have access to or do not seek regular Pap tests get this vaccine, it will have limited impact,” Dr. Harmon J. Eyre, chief medical officer of the Society, said in a statement announcing the new guidelines on the use of the prophylactic HPV vaccination to prevent cervical cancer and cervical intraepithelial neoplasia (CIN).
The guidelines emphasized that whether or not a woman has been vaccinated, she should continue to be screened for CIN and for cancer. “As HPV vaccination for the prevention of cervical cancer is introduced and promoted, it remains critical that women undergo regular screening even if they have been vaccinated,” Dr. Eyre said in the statement.
The guidelines were based on a formal review of the available data on HPV vaccination conducted by an expert panel convened by the ACS and are published in CA: A Cancer Journal for Clinicians (CA Cancer J. Clin. 2007;57:7–28).
The currently available vaccine is Gardasil, approved by the Food and Drug Administration in June 2006 for females aged 9–26 years to prevent conditions caused by HPV types 6, 11, 16, and 18, the HPV types covered in the vaccine (cervical cancer, condyloma acuminatum, cervical adenocarcinoma in situ, vulvar intraepithelial neoplasia grades 2 and 3, vaginal intraepithelial neoplasia grades 2 and 3, and CIN grades 1, 2, and 3). HPV types 16 and 18 cause about 70% of cervical cancers, and HPV types 6 and 11 cause about 90% of genital warts.
The guidelines concluded that there are not enough data to recommend either for or against universal vaccination of females aged 19–26 years in the general population. But deciding whether a woman in this age group should be vaccinated “should be based on an informed discussion between the woman and her health care provider regarding her risk of previous HPV exposure and potential benefit from vaccination.” Since the potential benefits are likely to lessen as a woman's number of lifetime sexual partners increases, women should “ideally” be vaccinated before potential exposure to genital HPV through sexual intercourse, the guidelines said.
The guidelines do not recommend HPV vaccination currently for women over age 26 or for men.
This year, the Society estimates that 11,150 women will be diagnosed with invasive cervical cancer in the United States, and that 3,670 women will die from cervical cancer. Most cervical cancers are caused by HPV infections, with about 70% caused by HPV types 16 and 18, which are included in Gardasil. Approximately 500,000 precancerous lesions are diagnosed annually in the United States, of which about 50%–60% can be attributed to HPV 16 and HPV 18.
A substantial, long-term impact of the vaccine on cervical cancer rates is not expected to be evident until the young girls being vaccinated reach the age of 48, the median age at which women are diagnosed with cervical cancer, the guidelines said. Ultimately, the impact on cervical cancer will be affected by factors that include coverage in at-risk populations and durability of protection. But in the short term, vaccination could potentially have a beneficial impact in terms of lower numbers of HPV infections leading to a reduced number of women with abnormal Pap smears that require a work-up and treatment, fewer abnormal Pap results, and fewer referrals for colposcopy, cervical biopsy, and genital warts (HPV 16, 11, 6, and 18 cause about 40% of histologically confirmed CIN).
The guidelines focus on Gardasil but will be updated as new vaccines become available and are approved. A second HPV vaccine, Cervarix, is not yet approved.
HPV vaccination was included for the first time in the 2007 recommended immunization schedule for children and adolescents, released earlier in January by the Centers for Disease Control and Prevention, the American Academy of Pediatrics, and the American Academy of Family Physicians. The three-dose series of HPV vaccine is recommended for girls aged 11–12 but can be started at age 9; catch-up vaccination is recommended for girls and women 13–26 years old who have not been vaccinated or have not received all three injections.