Abstract
INTRODUCTION: In this review and meta-analysis we aimed to investigate whether human papilloma virus (HPV) vaccination administered after excisional treatment of cervical intraepithelial neoplasia (CIN) is associated with a reduced risk of recurrence of CIN grade 2 or worse (CIN2+). MATERIAL AND METHODS: We performed a systematic literature search in three online databases through June 2021. Observational studies and randomized controlled trials (RCTs) were eligible for inclusion if the prophylactic HPV vaccine was administered after excisional treatment for histologically verified CIN. Only English language literature was included. The primary outcome measure was recurrence of CIN2+ after treatment. A meta-analysis was performed using fixed and random-effects models, and results were reported as pooled odds ratios (OR) with 95% confidence intervals (95% CI). Quality assessment was performed using ROB2-tool for RCTs and ROBINS-I for observational studies. The protocol was registered in PROSPERO (CRD42021238257). RESULTS: A total of 1561 studies were identified, of which nine, including 19 971 women, were included. Two studies were RCTs and seven were observational studies. Using the fixed-effect model on the two RCTs, the OR for recurrence of CIN2+ was 0.29 (95% CI 0.16-0.53). Due to considerable heterogeneity in observational studies, the random-effects model was used to estimate pooled OR for CIN2+ recurrence in these studies. Thus, using unadjusted data from observational studies, the OR for CIN2+ recurrence was 0.35 (95% CI 0.18-0.67), whereas when using adjusted data, the OR for CIN2+ recurrence was 0.54 (95% CI 0.21-1.35). However, quality assessment revealed a serious risk of bias for the majority of the studies included. CONCLUSIONS: HPV vaccination post-treatment was associated with a significantly reduced risk of CIN2+ recurrence when using unadjusted estimates from observational studies and RCTs. We found no significant effect of HPV vaccination on risk of CIN2+ recurrence when using the outcome measure from observational studies with the least risk of bias. Large, well-designed randomized placebo-controlled trials are needed to determine whether post-treatment HPV vaccination should be recommended to all women undergoing excisional treatment for CIN.