How many cervical cancers have been prevented so far through screening in Ireland?

Posted on: 19 December 2025

The outcomes figured by the team give a solid support for the clear efficacy of cervical cancer screening in Ireland and beyond. The study has been published in the journal European Journal of Public Health.

Cervical screening is a life-saving public health intervention, and Ireland’s national programme, CervicalCheck, was introduced in 2008. One of the ironies of successful public health interventions is that, when they work well, their benefits are often invisible: with cervical screening and HPV vaccination, we do not see the cancers that are prevented. While we cannot directly count events that never happened, mathematical modelling allows us to estimate their impact. The purpose of this work was to answer a simple counterfactual question: how many cervical cancers have been prevented so far through screening? 

A methodology for estimating cancers prevented by such programmes has immediate utility. This work derives a model for estimating cancer prevented by screening, applied to data from Ireland’s organized national cervical screening programme since its introduction in August 2008 to August 2022. A novel Markov-chain model for human papilloma virus (HPV) induced cervical cancer was derived with realistic transition probabilities validated against literature estimates.

Ireland’s CervicalCheck publish rich data on their service, including the number of low grade, high grade, and HPV infections detected, and how many new cases are detected each year. This allows scientists to apply the model of how cases progress to this data, and estimate how these cases would have evolved in the absence of screening. And from this, we can estimate how many cancers the introduction of screening in Ireland has prevented.

Data from CervicalCheck and from the National Cancer Registry of Ireland (NCRI) was applied to estimate the number of cancers prevented by screening, changes in Irish cancer detection since the implementation of screening, and treatment costs saved by screening. Since its inception in 2008, the modelling in this work suggests that CervicalCheck has prevented an estimated 5557 cancers (95% confidence interval: 5114–6000 cancers) and saved €102 million in future treatment costs (95% confidence interval: e94–110 million) not including inflation costs.

Additionally, 48:8% (95% confidence interval: 41.4%–56.2%) of all cervical cancers in Ireland have been detected through screening between 2008 and 2022. National screening in Ireland has been highly effective at reducing future cervical cancers, and detecting asymptomatic cancers. The model outlined here has direct future applicability for the assessment of national and regional cervical cancer screening programmes.

KEY FINDINGS FROM THE STUDY

The major finding from the team is that we estimate that cervical cancer screening in Ireland prevented over 5500 lifetime cervical cancers between 2008 and 2022 alone, by detecting issues that would in time have likely become cancer. That is thousands of women and families across Ireland over time who will no longer have to suffer a challenging illness, and a win for public health. We also have a powerful tool that can be applied in countries across the world to estimate what we cannot count. Public health is too often a victim of its own success, so having a means to quantify the hidden victories of these measures is a real positive.

The team has found that while cervical cancer rates were climbing in Ireland from 1994, they now appear to be falling even as the Irish population increases, with 48:8%±7:4% of all cervical cancers diagnosed being detected by screening since 2009. It is likely that cervical screening has detected earlier cancers prior to their clinical manifestation, rendering them more amenable to treatment.

David Robert Grimes, co-lead author and Assistant Professor in Biostatistics, Institute of Population Health, School of Medicine, said:

“ We can't measure things that did not happen, but we can apply mathematical modelling to see what would likely have transpired if screening did not exist. This allows us to quantify the benefits of screening in general, and apply that model to the Irish population. To answer the question of how many life-time cancers screening prevent, we have to ask a counterfactual question: if there was no screening, how would things have turned out for women with cervical abnormalities? This is a dark "what-if", but using mathematical techniques and understanding the progression of HPV infection to cervical abnormalities to cancer, we can answer this question both in the abstract, and then apply it to specific data.”

To the researchers’ knowledge, the team believe that this study is a very novel method to answer an important public health question, and flexible enough to use not just in Ireland, but around the world.

Assistant Professor Grimes, finalised by saying:

 "Public health interventions like screening and vaccination are too often victims of their own success, because when they work their victories are largely invisible. This new analysis illuminates the reality that cervical screening is highly effective to preventing cancers, and underscores the clear importance and effectiveness of the Irish national programme."

Read: You can read the full paper: ’A method of estimating cervical cancers prevented by the introduction of national screening in Ireland’ in European Journal of Public Health, at the following link:

https://academic.oup.com/eurpub/advance article/doi/10.1093/eurpub/ckaf225/8383798?searchresult=1

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