The findings, published in the medical journal BMC Medicine, are the first in the world to show that a population-based HPV vaccination program has resulted in a fall in cervical abnormalities within five years of implementation.
'We found that the greatest vaccine effectiveness was observed for the women vaccinated at the youngest ages,' said Executive Director of VCS Professor Marion Saville. Previous Australian research had found rates of these abnormal cells, which are detected on Pap tests, were falling in young women, but this new study proves that this is due to the HPV vaccine.
The AIHW linked the National HPV Vaccination Program Register with Victoria's Pap test Register and undertook complex statistical analysis to evaluate the effectiveness of the HPV vaccine against cervical abnormalities in women in schools.
The study found that women vaccinated with all three doses in the school cohorts of the catch-up program (aged 12-17 years in 2007) have a 48% lower rate of the most serious precancerous abnormalities than unvaccinated women.
'And we expect that over the next five years, the effect of the vaccine will increase as women vaccinated at 12 to 13 years move through the screening program. This is because these younger women are less likely to have been sexually active before vaccination.'
'Australia is in a unique position to evaluate the impact of the HPV vaccine at the population level because it was one of the first countries to introduce a publicly funded national HPV vaccination program in April 2007,' said AIHW spokesperson Justin Harvey.
The vaccination program targets girls aged 12 to 13 on an ongoing basis, with boys of the same ages also offered the vaccine from this year. Two-year catch-up programs were offered to girls aged 14 to 17 in schools and women aged 18 to 26 in community-based settings.
HPV vaccines are highly effective at preventing infection with certain HPV types that cause about 70% to 80% of cervical cancers worldwide and in preventing related cervical abnormalities, which are precursors to cervical cancer.
The research article, which presents data from the school-based program on population-level vaccine effectiveness against cervical abnormalities in Victoria, can be found at http://www.biomedcentral.com/1741-7015/11/227