Association Between HPV Vaccination and Cervical Dysplasia Severity in HPV-Positive Women

Background: Although HPV vaccination is highly effective in the primary prevention of cervical cancer, its potential role in women already diagnosed with HPV-associated cervical dysplasia remains uncertain. This study aimed to evaluate the association between post-diagnosis HPV vaccination and short-term clinical outcomes in HPV-positive women with cervical dysplasia. Methods: Women aged ≥18 years with abnormal cervical screening results suggestive of squamous intraepithelial lesions and high-risk HPV positivity were retrospectively evaluated. High-grade disease was defined as histologically confirmed CIN2/3. HPV vaccination (9-valent) was recommended to all eligible patients at the time of diagnosis. Vaccination status was primarily analyzed as vaccinated (≥1 dose) versus unvaccinated; additionally, dose-stratified analyses (0, 1–2, and 3 doses) were performed to explore potential dose–response relationships. Results: A total of 392 women were included (173 unvaccinated and 219 vaccinated). At 12 months, regression occurred in 51.1% of vaccinated patients compared with 41.0% of unvaccinated women (OR 1.50, 95% CI 1.02–2.20, p = 0.04). A dose–response pattern was observed, with regression rates of 41.0% in unvaccinated patients, 46.1% in partially vaccinated patients, and 54.6% in fully vaccinated patients (p for trend = 0.012). In the HSIL subgroup, regression occurred in 49.0% of vaccinated women versus 33.8% of unvaccinated patients (OR 1.88, 95% CI 1.01–3.52, p = 0.047). When stratified by treatment modality, vaccination was significantly associated with higher regression in the non-LEEP cohort (OR 1.67, p = 0.04) but not in the LEEP cohort (p = 0.22). In multivariable analysis adjusting for age, smoking, HPV genotype, baseline histopathologic grade (CIN1 vs. CIN2/3), and treatment modality, HPV vaccination remained independently associated with regression (aOR 1.55, 95% CI 1.05–2.30, p = 0.028). Conclusions: Post-diagnosis HPV vaccination was associated with a higher probability of cervical dysplasia regression at 12 months, particularly among women with baseline HSIL. These findings suggest that HPV vaccination may provide a beneficial adjunct effect in the clinical management of HPV-associated cervical dysplasia. Prospective studies are required to confirm these observations and clarify the mechanisms underlying this association.