Many vaccinated women have reached the age of first screen. Screening registers have shown that the incidence of CIN2 or worse (CIN2+) decreases substantially as a consequence of vaccination and therefore, countries need to rethink the age of the first screen as well as the primary screening instrument. Data sources that can inform screening strategies for vaccinated women include randomized screening trials performed in vaccinated women, and screening cohorts and registries in which the occurrence of prevalent and incident genotype-specific HPV infections and CIN are estimated.
An overview of the evidence in the literature will be given. Furthermore, the Dutch POBASCAM and VUSAscreen trial will be used to illustrate how vaccines with protection against HPV 16/18 and 16/18/31/33/45/52/56 are expected to influence the HPV prevalence and the positive predictive value for detection of CIN3+ at the first screen. The impact of vaccination on CIN3+ will be calculated under the assumption of a hierarchical and proportional classification of type-specific CIN lesions, and by means of a statistical approach that assumes that type-specific CIN3+ risks are independent.
An important measure for advising on the age of first screen is the positive predictive value for detection of CIN3+. The positive predictive value may decrease substantially when vaccinated cohorts enter screening which supports an increase of the starting age of screening.