Cancer-causing infections tumble thanks to mass vaccination of girls

Rates of HPV infections in Australian women have dropped by 92 per cent in the past eight years.

Precancerous cervical lesions have also tumbled, with diagnoses dropping by 70 per cent in Australian women aged under 20 and by about 50 per cent in women aged between 20 and 24.

Genital warts are also on the decline. Researchers estimate that diagnoses of the sexually transmitted infection have declined by about 70 per cent in Australian women in recent years.

The findings, published in The Lancet Public Health Journal on Thursday, examined the health outcomes of 60 million people who had been vaccinated in 14 high-income countries, including Australia.

The global research analysis, which reviewed the findings of 65 studies from across the world, found countries with vaccination programs in place are rapidly lowering the rate of the highly contagious disease along with precancerous lesions and genital warts.

"Our results provide strong evidence that HPV vaccination works to prevent cervical cancer in real-world settings," Melanie Drolet of Laval University in Quebec, who led the work, said.

There was good news for teenage boys and men too.

Diagnoses for genital warts among unvaccinated teenage boys, aged 15 to 19, living in places including Australia, Canada and the UK, have almost halved in five years, while men aged between 20 and 24, had seen a drop of about 34 per cent in the sexually transmitted infection.

This suggests that vaccinating girls and young women can protect boys and men too thanks to herd immunity, researchers said.

Two strains of HPV, types 16 and 18, are responsible for more than 70 per cent of cervical cancers and genital warts. Researchers found incidence of both significantly reduced after vaccination with the drug known as Gardasil.

The free national HPV vaccination program was first rolled out to Australian schoolgirls aged 12 to 13 in 2007 as a three-dose course and was expanded to boys in 2013.

In 2017, a new vaccine known as Gardasil 9 was introduced which can prevent 90 per cent of cervical cancers worldwide, compared with 70 per cent with the original.

Associate Professor Julia Brotherton, who was a co-author of the research and is medical director of Population Health at the VCS Foundation in Melbourne, said the findings reinforced the importance of vaccinating more than one age group for "biggest and fastest impacts".

"The vaccines create really great herd protection effects and these are greatly strengthened by vaccinating multiple cohorts at once," she said.

"This causes a greater interruption in circulation of the virus and accelerates the disease prevention benefits."

But the effectiveness of the vaccination declined as a person aged as many had already been exposed to the infection through sexual transmission.

"In Australia, vaccinating up into older age groups is recommended for those who have immune suppression, men who have sex with men, and should be considered for women after treatment of cervical precancers," Associate Professor Brotherton said.

"But women also need to remember that if you are or have ever been sexually active, cervical screening is the best way to protect yourself against cervical cancer."

Last year, a national forecast predicted cervical cancer would become a rare disease in Australia within just two years and rendered so uncommon by 2028, it will be deemed eliminated as a public health problem for the first time anywhere in the world.

"Australia remains a world leader in cervical cancer prevention and as long as we maintain our strong immunisation program and improve the reach of our cervical screening program to all women we certainly hope to be one of the first countries to reach the elimination threshold," Associate Professor Brotherton said.

But more work is needed. Cervical cancer rates were still more than double in Aboriginal and Torres Strait Islander women, with the death rate three times higher than for non-Indigenous women, Associate Professor Brotherton said.

"It is really critical that we keep our eye on equity and making sure the vaccine is reaching all girls and boys and that screening is acceptable and easy to access for all women," she said.