Human papillomavirus prevalence in first, second and third cervical cell samples from women HPV-vaccinated as girls, Denmark, 2017 to 2024: data from the Trial23 cohort study

BACKGROUNDDanish women vaccinated with the 4-valent human papillomavirus (HPV) vaccine (HPV types: 6/11/16/18) at age 14 in 2008 reached screening age in 2017, allowing assessment of long-term effects on prevalence, persistence and incidence of HPV infections.AIMTo examine the HPV status of cervical samples over time among women vaccinated as girls.METHODSBetween February 2017 and February 2024, residual material from cytology-analysed samples collected through the 'Trial23' study, part of the national screening programme, was tested for HPV16/18 and non-vaccine high-risk (HR) HPV types. Prevalence in first, second and third samples, and persistence and incidence between samples were calculated.RESULTSOver 7 years, 8,659 women provided at least one sample, 5,835 at least two and 2,461 at least three. In 7,800 vaccinated women, HPV16/18 prevalence was 0.4% (95% confidence interval (CI): 0.2-0.5), 0.3% (95% CI: 0.1-0.4) and 0.2% (95% CI: 0.0-0.4) in three consecutive samples. Prevalence of non-vaccine HR HPV was 32% (95% CI: 31-33), 28% (95% CI: 27-29) and 31% (95% CI: 29-33). Persistence of HPV16/18 and non-vaccine HPV among vaccinated women was 40% and 53%. In adjusted analyses comparing vaccinated vs unvaccinated women, incidence was significantly lower for HPV16/18 (adjusted relative risk (aRR) < 0.10) while incidence of non-vaccine HR HPV types was higher (aRR: 1.66; 95% CI: 1.12-2.45). No significant difference was observed for persistence.CONCLUSIONOur study provides real-world evidence of stable protection against HPV16/18 infections in women vaccinated as girls. Less intensive screening seems reasonable until women vaccinated with the 9-valent vaccine reach screening age, when screening should be reconsidered.