Incidence of cervical precancerous lesions and cervical cancer in Denmark from 2000 to 2019: Population impact of multi-cohort vaccination against human papillomavirus infection

In Denmark, vaccination against human papillomavirus (HPV) has been implemented in the children's vaccination program (January 2009) and in multiple catch-up cohorts (October 2008 in girls 13-15 years and in August 2012 in women up to 27 years). In the present study we estimate incidence of cervical intraepithelial neoplasia grade 3 (CIN3), adenocarcinoma in situ (AIS), squamous cell carcinoma (SCC) and adenocarcinoma (AC) during 2000-2019. All cases of CIN3 and AIS were identified from the nationwide Pathology Data Bank, while SCC and AC were identified from the Danish Cancer Registry. We calculated age-standardized incidence rates and estimated annual percentage change (EAPC) with corresponding 95% confidence interval (CI) for the periods before vaccination implementation (2000-2005), early after implementation of childhood HPV vaccination and the first catch-up vaccination program (2006-2012), and after implementation of the second catch-up program (2013-2019). For CIN3 and AIS, age-specific incidence rates and EAPCs were calculated. An increasing age-standardized incidence was observed before introduction of HPV vaccination (2000-2005) for CIN3 [EAPC(CIN3): 3.0 (95% CI 1.7 to 4.3)] and AIS [EAPC(AIS): 3.5 (95% CI 0.7 to 6.4)]. In the most recent period (2013-2019), following implementation of the second catch-up program, a decrease was observed for both CIN3 [EAPC(CIN3): -6.5 (95% CI -8.3 to -4.8)], AIS [EAPC(AIS): -8.7 (95% CI -12.3 to -5.1)] and for SCC [EAPC(SCC): -3.9 (95% CI -7.5 to -0.2)]. In this study we document a decrease in the incidence of CIN3, AIS and SCC in the period after implementation of multi-cohort HPV vaccination in Denmark.