High-grade cervical lesions after vaccination against human papillomavirus: A Danish cohort study

Introduction: It is pertinent to evaluate the impact of vaccination against human papillomavirus (HPV) in real life. The aim of the study was to evaluate the real-life impact of HPV vaccination in the first birth cohort of Danish women offered free HPV vaccination as girls and invited to screening at the age of 23 years.

Material and methods: Women born in 1993 were offered free HPV vaccination at the age of 15 years but women born in 1983 have never been offered free HPV vaccination. We followed these two birth cohorts for 10 years from the age of 15 to after their first invitation to screening, and compared the risk of high-grade cervical intraepithelial neoplasia (CIN). Data were obtained from Danish national health registers.

Results: Vaccination coverage was 91% in the 1993 birth cohort and <0.1% in the 1983 cohort. Screening coverage was close to 80% in both cohorts. CIN2+ was detected in 4% of the 15 748 screened women born in 1983 and in 3% of the 19 951 screened women born in 1993. The risk of high-grade CIN was reduced by about 30% in the 1993 cohort compared with the 1983 cohort; for CIN2+ relative risk 0.74 (95% CI 0.66-0.82) and for CIN3+ relative risk 0.68 (95% CI 0.58-0.79).

Conclusions: This study investigated the real-life impact of quadrivalent HPV vaccination by comparing a cohort of women offered HPV vaccination with a cohort of women not offered HPV vaccination. The observed decrease in the detection of high-grade cervical lesions following HPV vaccination is in line with results from the randomized trials and has important implications for future cervical screening of HPV vaccinated cohorts.