Abstract
BACKGROUND: Human papillomavirus (HPV) infection remains the most prevalent sexually transmitted viral infection worldwide and a major etiologic factor for cervical and other anogenital cancers. HPV-related precancerous lesions continue to represent a substantial clinical and epidemiological burden. OBJECTIVE: We aim to assess the effects of nine-valent HPV vaccination on viral clearance, genotype distribution, and lesion regression among HPV-positive women who were unvaccinated in childhood. METHODS: We enrolled 461 women between January 2020 and August 2025 to the study who presented with abnormal cytology, positive hrHPV tests, or abnormal colposcopic findings. Participants underwent LBC, HPV genotyping, colposcopy, and biopsy or LEEP when indicated. The vaccinated cohort (n = 351) received the Gardasil®9 series (0-2-6 months), while 110 women served as unvaccinated controls. Statistical analyses were performed using R software (v4.4.2) with a significance threshold of α = 0.05. RESULTS: Following vaccination, HPV positivity for any genotype was significantly lower in the vaccinated group than in the control group (29.3% vs 56.4%, p < .001). Clearance of Gardasil-specific genotypes occurred in 83.5% of vaccinated women compared with 63.6% in the controls. Complete remission was higher in the vaccinated group (70.7% vs 43.6% in the control group). Persistence of identical HPV genotypes was markedly reduced after vaccination (8.5% vs 27.3%). CONCLUSIONS: Nine-valent HPV vaccination significantly enhanced viral clearance and reduced persistence and recurrence of high-grade squamous intraepithelial lesions (HSIL) among previously unvaccinated HPV-positive women. These findings support extending vaccination recommendations to adult HPV-positive patients as an adjunctive strategy to surgical and cytologic management.