Low-Grade Cervical Intraepithelial Neoplasia (CIN1) Evolution: Analysis of Opportunistic Preventive Vaccination Role

Background: Low-grade cervical lesions have a high percentage of clearance in young women, even if 71–82% of low-grade intraepithelial lesion/atypical squamous cells of undetermined significance (LSIL/ASCUS) reported a High-Risk Human Papillomavirus (HR-HPV) infection, which correlates with an increased risk of Cervical Intraepithelial Neoplasia (CIN)2+. The immunogenic effect of the anti-HPV vaccine appears to be significant. The aim of the study is to evaluate the effect, two years after the diagnosis, of the anti-HPV preventive vaccination on patients with low-grade cervical lesions. Methods: We collected clinical, colposcopic, histological, and virological data from patients aged 21–45 years who attended the colposcopy service of the department of Obsetrics and Gynecology of IRCCS Foundation Policlinico San Matteo, Pavia, Italy. In the 2005–2019 period and had a low-grade pap-smear. Results: We enrolled 422 women consecutively, divided into two groups (vaccinated and not vaccinated) for the retrospective analysis. The rate of persistence and progression of CIN were higher in the not-vaccinated group (p = 0.019). The relative risk (RR) to develop CIN2+ during follow-up vs. the the CIN1 persistence was 1.005 (95% Confidence Interval—CI 0.961–1.051) vs. 0.994 (95% CI 0.994–1.018) for age, 3.472 (95% CI 1.066–11.320) vs. 1.266 (95% CI 0.774–2.068) for non-vaccinated, 0.299 (95% CI 0.088–1.018) vs. 0.518 (95% CI 0.242–1.109) for HIV status negative, respectively. Analyzing the time to negativity, the odds ratio (OR) was 1.012 (95% CI 1–1.024) for age and 1.591 (95% CI 1.223–2.069) for vaccination; on the other hand, considering the relationship between the time to negative and the HPV genotypes contained in the 9-valent HPV vaccines, the OR was 1.299 (95% CI 1.026–1.646) for at least one of these at recruitment and 0.631 (95% CI 0.471–0.846) at follow-up. Furthermore, the presence of at least one of the HPV genotypes targeted by the HPV nonavalent vaccine is a key indicator of the risk of progression to CIN2+: OR was 3.443 (95% CI 1.065–11.189) for the presence of at least one HPV genotype at enrollment and 5.011 (95% CI 1.899–13.224) for the presence of at least one HPV genotype at follow-up, respectively. Conclusions: We reported in a retrospective study the benefit of anti-HPV vaccination in promoting negativity and increasing low-grade cervical lesions regression.