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What is next on the HPV vaccine horizon?
As clinicians begin to integrate use of the first cervical cancer vaccine (Gardasil, Merck & Co.; Whitehouse Station, NJ), the Food and Drug Administration (FDA) is set to review the application for a second vaccine.
GlaxoSmithKline USA, of Philadelphia, submitted the application for Cervarix, its human papillomavirus (HPV) vaccine candidate, in March 2007. If licensed, the vaccine will be indicated for the prevention of cervical cancer and precancerous lesions associated with the most common cancer-causing HPV types. The application includes a "considerable amount" of data for virus types 16 and 18 that cause 70% of cervical cancer cases worldwide, as well as data for other virus types that can lead to cervical cancer, says Barbara Howe, MD, vice president and director of GlaxoSmithKline's North American vaccine development organization.
Research details protection
Published research indicates that the vaccine demonstrated protection up to 4.5 years against persistent infection with HPV 16 and HPV 18 and protection from precancerous lesions.1 Protection also was demonstrated against infection with the third and fourth most prevalent cancer-causing types of HPV, types 45 and 31.1 More recent findings show that the cervical candidate vaccine, formulated with its proprietary adjuvant system, AS04, induced higher antibody levels and immune memory response compared to a similar HPV vaccine composition formulated with an aluminum hydroxide adjuvant.2
What about men?
Gardasil, which was approved in June 2006, targets four types of HPV: types 6, 11, 16, and 18. Guidance from the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) states that the vaccine be routinely given to girls when they are 11-12 years old.3 According to the ACIP recommendation, three doses of the new vaccine should be routinely given to girls when they are ages 11 to 12; however, the vaccination series can be started as early as age 9 at the discretion of the health care provider. Females ages 13-26 also may receive the vaccine, according to the ACIP recommendation.
About one in four U.S. females between the ages of 14 and 59 may have HPV, according to results of the first national estimate of the infection.4 But what about men? HPV infection is highly prevalent in sexually active men as well, according to a systematic literature review.5
Tampa researchers eye male role
Researchers at the Lee Moffitt Cancer Center & Research Institute, with headquarters at the University of South Florida in Tampa, are looking at men's roles in spreading HPV. The four-year study, funded by the National Institutes of Health, is designed to determine the incidence and persistence of type-specific penile HPV infections, measure the humoral immune response to HPV infection, and assess the factors independently associated with acquisition, persistence, and clearance of type-specific HPV infections in men. Soon-to-be published data indicate a high HPV prevalence in men, with little change in prevalence across the age span.6
To date, vaccine research information only is available on antibody levels in boys, which are similar to those seen in their female counterparts, says Khalil Ghanem, MD, assistant professor of medicine and associate fellowship program director in the Division of Infectious Diseases at Johns Hopkins University School of Medicine in Baltimore. Ghanem presented information on HPV vaccines at the recent Contraceptive Technology conference in Washington, DC.
HPV studies continue
Efficacy studies of the quadrivalent vaccine in men are ongoing, Ghanem says. They include a heterosexual male cohort evaluating the efficacy of the quadrivalent vaccine for preventing genital warts and a gay male cohort in evaluating the efficacy of the quadrivalent vaccine in preventing anal carcinoma. With no data yet available, the Gardasil vaccine is not currently recommended for males, he notes. "If the quadrivalent vaccine lives up to expectations in men, it will provide direct benefit against genital warts and against anal cancer," says Ghanem. "In addition, it will likely provide indirect benefit to unvaccinated women by decreasing their likelihood of exposure to HPV 6, 11, 16, and 18 if they come into contact with a man who has been vaccinated."
It will be virtually impossible to guarantee 100% vaccine uptake in women, says Ghanem. This fact makes it imperative that men be vaccinated to increase the likelihood that the unvaccinated women will not be exposed. "However, all of this is dependent on the vaccine being efficacious in men," Ghanem states. "We await the data."