#Grand Rounds

Bivalent HPV Vaccination: Dramatic Reduction in Prevalence of Cervical Disease at Age 20

BACKGROUND AND PURPOSE:

In 2008 Scotland initiated a national immunization program against HPV
- Bivalent vaccine | girls ages 12-13
Palmer et al. (The BMJ, 2019) aimed to quantify the effect of this program on cervical disease at age 20

Retrospective population study
Participants
- Women born between January 1^st, 1988 and June 5^th, 1996 who had liquid-based cytology with image assisted screening) result recorded at age 20
Primary outcome measures
- Effect of vaccination on cytology results and associated histological CIN diagnoses at age 20
Classification based on British Association for Cytopathology and NHS cervical screening program (Table 1 provides an easy comparison to Bethesda system)
Researchers also investigated herd protection
- Compared the disease rates among unvaccinated women in the 1991-92, 1993-4, and 1995-96 cohorts with unvaccinated women in the 1989-90 cohort (control group prior to national vaccine program)
Statistical analysis: Logistic regression

138,692 women included
When compared to unvaccinated women, vaccinated women
- CIN grade 3 or worse: 89% reduction (95% CI, 81% to 94%)
  - From 0.59% to 0.06%
- CIN grade 2 or worse: 88% reduction (95% CI, 83-92%)
  - From 1.44% to 0.17%
- CIN grade 1: 79% reduction (95% CI, 69% to 86%)
  - From 0.69% to 0.15%
Younger age at immunization was associated with an increase in vaccine effectiveness for CIN grade 3 or worse
- Vaccinated age 12-13: 86% reduction (95% CI, 75% to 92%)
- Vaccinated age 17: 51% reduction (95% CI, 28% to 66%)
Found evidence for herd protection against high-grade cervical disease in unvaccinated girls in the 1995 and 1996 cohort
- Even in unvaccinated women in the 1995-96 cohort, there was a reduction in CIN compared with unvaccinated women in 1988-90.

Bivalent HPV vaccine is highly effective
- Should result in decreased cervical cancer rates
- Study demonstrated herd protection in unvaccinated women
Study results consistent with reduced prevalence of high-risk HPV in Scotland

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