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National vaccination program reduced HPV prevalence among women
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A national government-funded vaccination program significantly lowered the prevalence of HPV among women in Australia, researchers have found.
According to the report published in the Journal of Infectious Diseases, Australia was the first country to implement such a program, meant to prevent cervical cancer. From April 2007 to December 2008, free HPV vaccination was offered to girls aged 12 to 17 years in a school-based program. General practitioners offered free vaccination to other women aged younger than 26 years.
Sepehr Tabrizi
“The HPV vaccination program in Australia has resulted in a 77% decrease in prevalence of vaccine-targeted HPV genotypes just four years after the program’s commencement,” Sepehr Tabrizi, PhD, senior research scientist in the department of microbiology at The Royal Women’s Hospital in Victoria, Australia, told Infectious Disease News. “Our data also suggest the possibility that there are signs of herd immunity, with the reduction in vaccine-related HPV genotypes among unvaccinated women.”
Tabrizi and colleagues compared HPV genoprevalence among a sample of women in the prevaccine period of 2005-2007 to the prevalence among another sample of women in the postvaccine period of 2010-2011. The women compared were aged 18 to 24 years and had attended family planning clinics for Pap screening.
The prevaccine sample included 202 women and the postvaccine sample included 404 women. Among the prevaccine group, the prevalence of any HPV genotype was 59.9% compared with 48% in the postvaccine group (P=.006). For the genotypes targeted by the vaccine, the seroprevalence was 28.7% prevaccine and 6.7% postvaccine.
When stratified according to self-reported vaccination status, vaccinated women had the lowest prevalence of HPV, and only 5% of these women had a vaccine genotype in the postvaccine group. There also was a reduction in HPV prevalence of the vaccine genotypes in unvaccinated women postvaccine, in which the prevalence was 15.8%.
“The substantial decrease in prevalence of genotypes, including types that are responsible for 70% of cervical cancers, should, in time, translate into reductions of HPV-related lesions and cancer,” Tabrizi said. “However, as there are still lesions and cancers that are caused by genotypes other than those covered by the vaccine, women should still continue to have Pap smears and vaccination.”
Tabrizi said that they are continuing to recruit women to reach a sample size that will allow them to estimate vaccine effectiveness according to the number of validated doses received, and to examine potential cross-protection and type replacement, as well as the extent of any herd immunity.
Disclosure: The researchers report financial relationships with Commonwealth Serum Laboratories, CSL Biotherapies, GlaxoSmithKline and Merck.
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