The Role of Adjuvant Nonavalent HPV Vaccination After LLETZ in Patients with Isolated CIN2: A Controlled Cohort Study

Women treated for cervical intraepithelial neoplasia grade 2 (CIN2) face an increased risk of disease recurrence due to persistent or newly acquired human papillomavirus (HPV) infections, suggesting a potential role for adjuvant HPV vaccination. While a growing body of literature evaluates the outcomes of HPV vaccination following a large loop excision of the transformation zone (LLETZ) for high-grade squamous intraepithelial lesions (CIN2-3), data specifically focused on isolated CIN2 remain limited. This study aims to evaluate the clinical efficacy of the nonavalent HPV vaccine (9vHPV) as an adjuvant strategy to reduce CIN2+ recurrence in women undergoing LLETZ for histologically confirmed, isolated CIN2.

Between November 2017 and November 2024, women undergoing LLETZ for histologically confirmed CIN2 received their first dose of adjuvant 9vHPV within one month of surgery. Patients who achieved double-negative co-testing (Pap test and high-risk HPV DNA test) at the 6-month post-LLETZ follow-up were included in the study group. Conversely, patients with at least one positive test result at 6 months were excluded to rule out residual disease. The study group underwent a subsequent Pap smear at 12 months and a full co-test at 18 months post-surgery; upon achieving negative results through the 18th month, patients returned to the organized screening program. The primary outcome was the recurrence rate, defined as histologically confirmed CIN2+ occurring more than 6 months post-treatment. It was compared against an unvaccinated historical control group treated with LLETZ prior to the study period. The secondary outcome evaluated the prevalence of HPV genotypes at baseline and at the time of recurrence.

In the vaccinated group, 3 women (2.03%) experienced CIN2+ recurrence compared to 6 women (5.71%) in the unvaccinated control group. This represents an absolute risk difference of 3.69% and a relative risk reduction of 64.6%, though the difference did not reach statistical significance via Fisher's exact test (p = 0.165). In the study group, two recurrences were detected at 18 months (associated cytologies: ASC-H and LSIL; genotypes: HPV 51/53 and 16, respectively) and one at four years (cytology: HSIL; genotype: HPV 33/58). In the control group, recurrences occurred at 12 months (n = 3), 18 months (n = 2), and four years (n = 1). Associated cytology revealed HSIL in three cases, ASC-H in one case, LSIL in one case, and ASCUS in the final case. The corresponding HPV genotypes were 16 (two cases), 18, 51, 31 and 56 (co-infection), and one case of high-risk HPV, not further genotyped.

Adjuvant 9vHPV administration after LLETZ for isolated CIN2 was associated with a clinically substantial lower absolute recurrence rate (2.03% vs. 5.71%, corresponding to a 64.6% relative risk reduction). Although this reduction did not achieve statistical significance (p=0.165) due to our small sample size and a low baseline recurrence rate in this isolated cohort, the effect size is highly comparable to broader CIN2+ studies. The study was likely underpowered to prove statistical significance, and larger multi-center studies are required to confirm the statistical value of adjuvant vaccination specifically in isolated CIN2 lesions.