Primary and secondary prevention in the Netherlands
Over the past decade, the options available for the prevention of cervical cancer have changed tremendously. The resulting policy questions have been addressed in our modeling work, which has directly influenced public health decision making.
Until recently, cytological screening – the so-called “Pap smear” – was the only means for cervical cancer prevention and population-based screening programs have reduced the incidence of cervical cancer in most developed countries. The finding that a virus, the human papillomavirus (HPV), is causally associated with cervical cancer has led to the development of two new prevention–methods: an HPV vaccine and HPV-based screening.
Currently, the Dutch screening program consists of five-yearly cytological screening among women aged 30 to 60. In 2016, the Netherlands will change to a primary HPV-based screening program among the same age-group. The screenings interval will however be extended to 10 years among women over the age of 40 who have a negative screening test result.
In addition to screening, an HPV vaccination program was implemented in 2009 – targeting girls aged 12 years, and with a catch-up program in 2009 only among girls aged 13-16 years. Almost 60% of girls in the targeted cohorts are vaccinated. The first vaccinated girls will enter the screening program in 2023. An important question is what the intensity of screening needs to be among vaccinated cohorts and how we can provide a screening program that takes into account the differential risk on cervical cancer in vaccinated women and unvaccinated women.
Our team has developed static and dynamic microsimulation models reflecting both the natural history of cervical cancer and the HPV infection. The models include parameters for the risk on HPV infection, the persistence or clearance of infection and the subsequent trajectory of (pre-) cancerous lesions. Furthermore, the interaction of vaccination and screening with the different infection/disease stages can be simulated. We have used these models to estimate (cost-) effectiveness of girls-only HPV vaccination and of HPV-based screening – and our results have been instrumental to the National Health Council in the decision-making process for a population-based vaccination program and a revision of the screening program. Building on these models, we are currently evaluating aspects of improvement for the vaccination program and its optimal integration with the screening program.
In addition to the mathematical modeling, we also perform epidemiological modeling for impact assessment and develop new statistical methods to answer more methodological research questions . In this manner we continuously improve our models.
Bogaards JA, Wallinga J, Brakenhoff RH, Meijer CJ, Berkhof J. Direct benefit of vaccinating boys along with girls against oncogenic human papillomavirus: bayesian evidence synthesis. BMJ. 2015 May 12;350:h2016. doi: 10.1136/bmj.h2016.
Coupé VM, Bogaards JA, Meijer CJ, Berkhof J. Impact of vaccine protection against multiple HPV types on the cost-effectiveness of cervical screening. Vaccine. 2012;30(10):1813-22.
Bogaards JA, Xiridou M, Coupé VM, Meijer CJ, Wallinga J, Berkhof J. Model-based estimation of viral transmissibility and infection-induced resistance from the age-dependent prevalence of infection for 14 high-risk types of human papillomavirus. Am J Epidemiol. 2010 Apr 1;171(7):817-25. doi: 10.1093/aje/kwp466. Epub 2010 Mar 15.