Effect of human papillomavirus vaccination on cervical cancer screening in Alberta (Canada)
Canadian Medical Association Journal August 2016
Jong Kim MD, Christopher Bell MPH, Maggie Sun MSc, Gordon Kliewer MN, Linan Xu MSc, Maria McInerney MSc, Lawrence W. Svenson PhD, Huiming Yang MD
A school-based program with quadrivalent human papillomavirus (HPV) vaccination was implemented in Alberta in 2008. We assessed the impact of this program on Pap test cytology results using databases of provincewide vaccination and cervical cancer screening.
We conducted a nested case–control study involving a cohort of women in Alberta born between 1994 and 1997 who had at least 1 Pap test between 2012 and 2015. Women with negative cytology results were controls. Women with low-grade (atypical squamous cells of undetermined significance or low-grade squamous intraepithelial lesion) and highgrade (atypical squamous cells, cannot rule out a high-grade lesion; or high-grade squamous intraepithelial lesion) cervical abnormalities were cases. Exposure status was assigned according to records of HPV vaccination. Odds ratios (ORs) for abnormal cytology results by vaccination status were adjusted for neighbourhood income, laboratory service, rural versus urban
residency, and age.
The total study population was 10 204. Adjusting for age, vaccinated women had a higher screening rate than unvaccinated women (13.0% v. 11.4%, p < 0.001). Among women who received full vaccination (≥ 3 doses), the adjusted OR for cervical abnormalities was 0.72 (95% confidence interval [CI] 0.63–0.82). For high-grade lesions, the adjusted OR was 0.50 (95% CI 0.30–0.85). With 2-dose HPV vaccination, the adjusted OR for cervical abnormalities was 1.08 (95% CI 0.84–1.38).
Quadrivalent HPV vaccination significantly reduced high-grade cervical abnormalities but required 3 doses. Vaccination
against HPV was associated with screening uptake. Population-based vaccination and screening programs should work together to optimize cervical cancer prevention.