THURSDAY, June 16, 2011 (HealthDay News) -- The introduction of a human papillomavirus (HPV) vaccination program in Australia led to a reduction in high-grade cervical abnormalities that are precursors to cervical cancer, a new study reports.
The researchers examined trends in high-grade cervical abnormalities, or HGAs, among women in Victoria, Australia before and after introduction of a national HPV vaccine program for all women aged 12 to 26 years.
The incidence of HGAs in girls aged 17 and younger who were screened fell by nearly 50 percent (from 0.80 percent to 0.42 percent) after the program was launched, but there was no decline in HGAs among older age groups.
"Our finding that the decrease in HGA incidence occurred in the youngest vaccination cohort before it occurred in the older, catch-up cohorts (who were more likely to have been previously sexually experienced) reinforces the appropriateness of the targeting of prophylactic HPV vaccines to preadolescent girls," Dr. Julia Brotherton, of Victorian Cytology Service Registries, and colleagues wrote in the report published in the June 18 issue of The Lancet.
"This is the first report of a decrease in incidence of HGAs within three years after the implementation of a population-wide HPV vaccination program," the study authors concluded.
But more work is needed to definitively link the HPV vaccine to lower incidence of precancerous cervical lesions, according to a journal editorial accompanying the study.
In their comment, Dr. Mona Saraiya and Susan Hariri, of the U.S. Centers for Disease Control and Prevention, wrote: "The not-so-cautious optimist in us wants to hail this early finding as true evidence of vaccine effect. However, individual-level vaccine status was not considered -- as it perhaps should have been in view of the availability of such data in Victoria, [Australia]."
And, "as stated by Brotherton and colleagues, linkage between vaccination and screening registers is needed to confirm these findings independently of possible bias by screening policy or practice changes. Indeed, more rigorous epidemiological studies are needed -- many are underway -- to increase our understanding of HPV vaccine effectiveness against cervical disease," Saraiya and Hariri added.
"A demonstrable reduction of the burden of cervical cancer -- the main goal of HPV vaccines -- will take several decades," the editorialists concluded.
Dr. Elizabeth A. Poynor, a gynecologic oncologist and pelvic surgeon at Lenox Hill Hospital in New York City, said: "This study is the first report on a large scale HPV vaccination program, outside the setting of a clinical trial.
"It demonstrates the important finding that an HPV vaccination program can lead to a lower incidence of significant HPV-related disease in young women. Because the study is not strong enough to demonstrate a "cause and effect," it therefore should be approached with cautious optimism," she added.
The U.S. National Cancer Institute has more about HPV vaccination.