Drastic Reductions in Cervical Disease Following HPV Vaccination
Just over a decade after routine vaccination of the Human Papillomavirus (HPV) was introduced, results out of Scotland have shown drastic reductions in pre-invasive cervical disease, a precursor for cervical cancer. HPV is responsible for nearly all cases of cervical cancer.
In 2008, Scotland introduced a national, school-based, immunization program against HPV, where girls aged 12 to 13 received the bivalent HPV vaccine targeting HPV types 16 and 18. Compared to a historical cohort of unvaccinated women born in 1988 (pre-vaccine; n=17 579), those who received the bivalent HPV vaccine born in 1995-1996 (n=18 031) showed an 89% reduction in prevalent cervical intraepithelial neoplasia (CIN) grade 3 or worse at age 20. Statistically significant reductions in all grades of CIN were observed, equating to vaccine effectiveness estimates of 80% or greater after routine immunization at age 12-13 years. These results are impactful, as CIN grade 3 is considered the best predictor of risk of invasive cervical cancer.
Interestingly, this study also showed evidence for herd protection against high grade cervical disease in unvaccinated women. Compared to unvaccinated women born in 1988 in the pre-vaccine cohort, those born in 1995 and 1996 who did not receive the vaccine had 63%, 67% and 100% reductions in CIN grade 1, CIN grade 2 and CIN grade 3, respectively.
The results out of Scotland show the value in high-uptake, routine immunization programs for HPV. They also encourage the potential of seeing similar disease reductions here in Canada, as Canada introduced a similar school-based HPV vaccination program around the same time. Taken together, these results give hope that with continued vaccination we could one day eradicate HPV infections and cervical cancer!