Alberta implemented a school-based immunization program in 2008. A three-year catch up program was added in 2009 and a vaccination program for boys was added in 2014. The current program involves three doses of the vaccine, which protects against 70 per cent of cases of cervical cancer.
It looked at women born between 1994 and 1997 who had at least one Pap test between 2012 and 2015.
The study involved 10,204 women, out of which 1,481 were cases while 8,723 were controls.
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Women with negative results were controls while women with low-grade and high-grade cervical abnormalities were cases.
Among the cases, 1,384, or 93.5 per cent, women had low-grade cervical abnormalities and 97 women had high-grade cervical abnormalities.
Within the total population group, 5,712, or 56 per cent, were unvaccinated and 4,492 were vaccinated with at least one dose before screening. The study showed that within the three-dose vaccinated group, 11.8 per cent had cervical abnormalities compared to 16.1 per cent of unvaccinated women.
“Three-dose HPV vaccination has demonstrated early benefits, particularly against high-grade abnormalities, which are more likely to progress to cervical cancer,” write the authors.
“Effective HPV vaccination will disrupt the balance of harms and benefits of cervical cancer screening.”
The study was conducted by researchers at the University of Calgary, the University of Alberta, Alberta Health and Alberta Health Services.