HPV vaccination is having a profound influence on HPV infection and associated disease in countries that have adopted national immunisation programmes. In Scotland -90% uptake of the bivalent vaccine in 12-13 year old girls has led to a reduction of around 85% of vaccine type infection in girls attending for first screen, as measured by an HPV genotyping assay with high analytical sensitivity. A significant impact of vaccine on CIN levels has also been observed. While this is hugely encouraging, the community is now faced with the challenge of how to effectively and efficiently screen vaccinated women given the radically altered prevalence of infection and disease.
Scotland has set up a national, longitudinal immunisation surveillance system to assess the impact of HPV vaccine on infection and disease, a national multi-disciplinary HPV research network (Scottish HPV Investigators Network – (www.shine.mvm.ed.ac.uk) and a national biobank of over 40 thousand samples designed to facilitate HPV research (www.shine.mvm.ed.ac.uk/archive). These endeavours have facilitated an integrated, national approach to ensure the development of primary (immunisation) and secondary (screening) disease prevention strategies are not considered in isolation. One strand of the associated research is to determine the impact of immunisation on the applicability and performance of primary cervical screening using molecular HPV testing through (1) the comparison of viral outcomes using epidemiologically orientated tests vs clinically validated tests, in immunised cohorts and (2) the assessment of performance of clinically validated HPV tests in immunised cohorts for the detection of CIN2+.
In vaccine surveillance studies, viral prevalence, as defined by epidemiologically orientated assays, may underestimate the impact of that HPV immunisation on clinically relevant levels of infection (CIN2+). While sensitivity and negative predictive value of primary HPV testing for CIN2+ remains high in immunised women; positive predictive value and specificity reduces – emphasising the need for effective triage(s). The seven-fold reduction of HPV 16/18 in immunised women may limit the utility of 16/18 typing as a triage strategy of HPV positive, vaccinated women.
Contemporary data which reflect the level and composition of both type specific HPV infection and associated disease in immunised women is essential to support the further planning of services for appropriate cervical disease management