The effect of HPV vaccination on the rate of high-grade cytology in 25-year-old women attending cervical screening in Ireland

Abstract

Introduction: Women vaccinated through the initial catch-up HPV vaccination programme (2011/12 to 2013/14) first became eligible for cervical screening in 2019 at age 25. This study aims to examine the changes in detection of HG cytology outcomes in 25-year-olds screened from 2010 to 2022 compared to population data on HPV vaccination in this group.

Methods: This was an ecological-type study. Cytology results from the CervicalCheck database from 2010 to 2022 (High Grade, Low Grade, and No Abnormality Detected) were plotted against data from the National Immunisation Office on the uptake of HPV vaccinations in females from 2010 to 2022.

Results: Vaccination rates in the catch-up programme were lower (44-70%) than for routine HPV immunisation at age 12/13 in 2010/11 (81%). The rate of high-grade cytology in 25-year-olds in 2015-2018 was 3.7% of all cytology tests taken in this age group. For the corresponding period from 2019 to 2022 (when vaccinated women were attending screening), the average percentage of HG cytology in 25-year-olds was 1.5%, representing a significant reduction in HG cytology proportions (p < 0.001).

Conclusion: This study provides early evidence of the potential impact of HPV vaccination on cervical disease in the Republic of Ireland. Despite lower vaccination uptake in the initial catch-up group, we are seeing early signs of the positive protective effect of HPV vaccination in women at the time of their first cervical screening test. Plans to incorporate individual-level HPV vaccination status for women on the cervical screening register will allow more detailed assessment of the impact of HPV vaccination.

Keywords: HPV vaccination; High-grade CIN.