Potential impact of introducing a nonavalent HPV vaccination.

<bold>Objective: </bold>To test the theoretical utility of incorporating nonavalent vaccination against HPV into a clinical setting.<bold>Methods: </bold>The present retrospective study included data from consecutive patients who underwent HPV-DNA testing between January 1, 1998, and December 31, 2015. Changes in the prevalence of different HPV types were assessed during three periods (T1, 1998-2003; T2, 2004-2009; and T3, 2010-2015) using XY analysis.<bold>Results: </bold>The study included a total of 13 665 patients. Overall, 1361, 5130, and 7174 patients were included in the T1, T2, and T3 periods, respectively. The quadrivalent vaccine would have potentially protected against HPV in 71.5% (973/1361), 46.5% (2385/5130), and 26.5% (1901/7174) of patients in T1, T2, and T3, respectively (P<0.001 for trend). The nonavalent vaccine could have protected against HPV in 92.5% (1259/1361), 72.3% (3709/5130), and 58.1% (4168/7174) of patients in T1, T2, and T3, respectively (P<0.001 for trend). The proportion of patients with genital dysplasia grade 2+ who did not have infections with HPV genotypes covered by the quadrivalent or nonavalent vaccines increased across the three periods (P<0.001 for trend). For all study periods, the protection provided by the nonavalent vaccine would have been superior to the quadrivalent vaccine (χ2 test P<0.001).<bold>Conclusion: </bold>The introduction of a nonavalent vaccine could improve protection against HPV infections and HPV-related genital dysplasia. [ABSTRACT FROM AUTHOR]