Oct. 15 (HealthDay News) -- New cases of genital warts have declined sharply since vaccination of teen girls and young women against the human papillomavirus (HPV) began in Australia in 2007, a new study has found.

Certain types of HPV are linked with the development of cervical cancer.

Researchers analyzed data on new clients receiving treatment for genital warts at the Melbourne Sexual Health Center between 2004 and 2008. During that time, the center had 36,055 clients, and genital warts were diagnosed in 10.6 percent of cases. The number of women under age 28 who were newly diagnosed with genital warts decreased by 25 percent each quarter throughout 2008, the researchers found.

Australia began providing free vaccinations with Gardasil for females ages 12 to 26 in 2007. In the period before the vaccinations began, new cases of genital warts rose by nearly 2 percent each quarter, the study authors noted.

The study also found that newly diagnosed cases of genital warts among young men fell by an average of 5 percent each quarter throughout 2008. Rates of newly diagnosed genital warts among older women and men didn't decline.

The findings are published in the Oct. 15 online edition of the journal Sexually Transmitted Infections.

"The magnitude of the reduction in women [under] 28 years indicates a potential for substantial reductions in wart-associated morbidity and costs, and has important implications for countries deciding between the [Gardasil and Cervarix] vaccine," the researchers wrote.

Gardasil protects against HPV types 6, 11, 16 and 18, while Cervarix protects against HPV types 16 and 18. Types 6 and 11 are associated with highly infectious genital warts, while types 16 and 18 are associated with cervical cancer.

SOURCE: Sexually Transmitted Infections, news release, Oct. 15, 2009