May 8, 2009
Cases of genital warts at a large Australian health clinic have plunged in the 12 months since the introduction of the Gardasil vaccine. The three-shot series protects against human papillomavirus (HPV) strains that cause 90 percent of genital warts and 70 percent of cervical cancer cases.
The Melbourne Sexual Health Center began to notice a decline in the number of cases of genital warts within six months of the vaccine's introduction there in mid-2007, said Professor Christopher Fairley, the clinic's director. The vaccine has also been distributed in Australia under the National Human Papillomavirus Vaccination Program since January 2008.
The center reviewed about 36,000 new patient contacts dating back to 2004. The number of female center patients with genital warts under the age of 28 fell to about half, while the number of cases among heterosexual men has fallen about 20 percent, Fairley said. The decline among women is the direct result of the vaccine, while heterosexual men are seeing a drop in cases because they are not being infected by women, Fairley noted.
The clinic has not seen a decline in the incidence of genital warts among gay men, suggesting that the observed drop can be attributed to the vaccination of women, Fairley said.
Fairley said the drop in genital warts supports the idea that Gardasil eventually will bring about a reduction in cervical cancer cases. "The abnormalities that the vaccine protects against in the cervix take much longer to appear," he said.
Fairley predicted that if the number of cases continues to drop by half each year, genital warts could eventually become a "historic phenomenon." "It won't take long and it's solely due to the vaccine," he said.