Rates of new genital wart infection in Australia have plummeted, research shows, in an early positive sign of the success of mass Gardasil vaccinations.
A study taking in patient data from sexual health clinics across the country has shown up to a 60 per cent drop off in new genital wart cases since 2007, when the anti-cancer vaccine was rolled out.
Gardasil works by preventing the transmission of four strains of the Human papillomavirus (HPV), two of which cause cervical cancer and two which cause genital warts.
Experts say while its effect on cervical cancer rates would take longer to materialise, the vaccine's ability to prevent a less serious though embarrassing problem was now clear.
"Genital warts are distressing to the patient, as well as being difficult and expensive to treat," said Professor Basil Donovan, head of the Sexual Health Program at the University of NSW's National Centre in HIV Epidemiology and Clinical Research.
"While we knew from clinical trials that the vaccine was highly effective, Australia is the first country in the world to document a major benefit for the population as a whole."
Free Gardasil vaccinations were offered to Australian girls and young women, aged 12 to 26 years, and about 80 per cent of those eligible are thought to have taken up the offer.
Researchers pooled data from eight sexual health clinics Australia-wide, covering 110,000 new patients and the period from 2004 to 2009.
About 6000 new cases of genital warts were detected and analysis revealed a 60 per cent drop-off among women aged under 27, while there was no change among older women or gay men.
Heterosexual men recorded a smaller decline in new genital wart cases of just over 30 per cent, the result of increased immunity among their younger female partners.
"The high coverage by the vaccination program has had a large, population-level impact on the incidence of genital warts in young Australian women," the research concluded.
"A more moderate impact for heterosexual men has presumably resulted from herd immunity."
Herd immunity theory proposes that, in diseases passed from person to person, it is more difficult to maintain a chain of infection when large numbers of a population are immune.
The research will be presented this week at an international HPV conference in Montreal.
Source: Sydney Morning Herald, 6 July 2010