TL;DR
A cohort study of Danish women vaccinated as girls found vaccine-covered HPV types 16 and 18 have been almost eliminated, with prevalence falling from about 15–17% pre-vaccination to under 1% by 2021. However, around one-third of women still carried high-risk HPV types not covered by the original vaccine, and new infections with these non-vaccine types were more frequent in vaccinated than in unvaccinated women.
What happened
Trial23 followed a birth cohort of women born in 1994 who were offered HPV vaccination in Denmark beginning in 2008 and reached cervical screening age in 2017. Embedded in the national screening programme, the study randomly allocated half of women in the study area to have residual cervical screening material HPV-tested and collected up to three consecutive cervical cell samples per woman between February 2017 and February 2024. HPV testing used Roche Cobas assays (with 1% of samples analysed on an Allplex assay after April 2023). The analysis focused on prevalence, persistence and incidence of vaccine-covered high-risk types (HPV16/18) and other high-risk HPV types. Results show that HPV16/18 infections have fallen to under 1% by 2021 among these vaccinated cohorts, while roughly one-third of women still tested positive for non-vaccine high-risk HPV types and new infections with those types occurred more often in vaccinated than unvaccinated women. The study covered samples from pathology departments representing about 55% of eligible Danish women.
Why it matters
- The large drop in HPV16/18 indicates strong population-level impact of the vaccination programme against the HPV types most commonly linked to cervical cancer.
- Persistence of non-vaccine high-risk HPV types in about one-third of women means continued cervical screening remains necessary for these cohorts.
- Higher incidence of non-vaccine high-risk types among vaccinated women highlights a need to monitor type-specific dynamics after vaccine introduction.
- Findings support reassessment of screening strategies for vaccinated generations — potentially less intensive but sustained screening is warranted.
Key facts
- Study population: women born in 1994 who reached screening age (23) in 2017 and were offered HPV vaccination starting in 2008.
- Pre-vaccination prevalence of HPV16/18 in comparable generations was reported at approximately 15–17%; in the vaccinated cohort this fell to less than 1% by 2021.
- About one-third of women in the study had infection with high-risk HPV types not covered by the original vaccine used.
- New infections with non-vaccine high-risk HPV types were more frequent in vaccinated versus unvaccinated women in the study.
- Trial23 collected up to three cervical cell samples per woman between 1 February 2017 and 29 February 2024.
- HPV testing was performed on residual SurePath samples mainly using Roche Cobas 4800/6800; 1% of samples were analysed with Seegene Allplex after April 2023.
- Denmark began free public vaccination with the 4-valent HPV vaccine in October 2008, briefly used the 2-valent vaccine in 2016, and switched to the 9-valent vaccine in November 2017.
- First-dose vaccine uptake in the Danish programme was reported at about 80–90%.
- The participating pathology departments covered roughly 55% of the Danish population of women aged 23–64 years included in the screening programme.
- In Denmark before vaccination, 74% of cervical cancers were associated with HPV16/18 and 26% with non-vaccine high-risk types.
What to watch next
- Ongoing surveillance of non-vaccine high-risk HPV type prevalence and incidence across subsequent screening rounds to detect shifts in type distribution.
- Reassessment of screening protocols for vaccinated cohorts to determine whether screening intensity can be safely reduced while maintaining cancer prevention.
- Long-term trends in cervical cancer incidence in these vaccinated birth cohorts (not confirmed in the source).
Quick glossary
- Human papillomavirus (HPV): A group of viruses, some of which can infect the genital tract; certain types are classified as high-risk because persistent infection can lead to cervical and other cancers.
- High-risk HPV (HR HPV): HPV types associated with a higher probability of progressing to precancerous lesions and cancer if infections persist.
- 4-valent / 9-valent vaccine: Vaccines that protect against multiple HPV types: the 4-valent covers four types (including 16/18), the 9-valent covers nine types, expanding protection against additional high-risk types.
- HPV DNA test (Cobas): A laboratory test that detects DNA from specific HPV types in cervical samples to identify current infection with high-risk HPV.
Reader FAQ
Did the study find that HPV16/18 infections were eliminated?
The study reports that prevalence of HPV16/18 among vaccinated women fell from about 15–17% pre-vaccination to under 1% by 2021, indicating near-elimination of these types in the cohort.
Are vaccinated women still being infected with other HPV types?
Yes. Around one-third of women had infections with high-risk HPV types not covered by the vaccine used earlier in the programme.
Does this mean vaccinated women can stop cervical screening?
No. The authors state that the persistence of non-vaccine high-risk HPV types supports continued, though potentially less intensive, screening for these generations.
What was the vaccine uptake in Denmark when the programme began?
First-dose coverage was reported at approximately 80–90% when the national programme began.
Home Eurosurveillance Volume 30, Issue 27, 10/Jul/2025 Article Research Open Access Like 0 Download Human papillomavirus prevalence in first, second and third cervical cell samples from women HPV-vaccinated as girls,…
Sources
- HPV vaccination reduces oncogenic HPV16/18 prevalence from 16% to <1% in Denmark
- Human papillomavirus prevalence in first, second and third …
- Denmark close to wiping out leading cancer-causing HPV …
- HPV16 and 18 nearly eliminated in vaccinated Danish …
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