Abstract
OBJECTIVE: Vaccine efficacy among previously exposed, but currently uninfected women, i.e., those who have serological evidence of a prior human papillomavirus (HPV) infection without corresponding detectable HPV DNA, remains incompletely defined. This meta-analysis assessed the serotype-specific efficacy of prophylactic HPV vaccination against HPV16/18 persistent infection (PI) and cervical intraepithelial neoplasia (CIN) among seropositive, DNA negative (SPDN) women enrolled to randomized controlled trials (RCTs) of HPV L1-based vaccines. METHODS: Searches were conducted on 08/16/20 on MEDLINE, Embase, Scopus and CENTRAL. RCTs of L1-based prophylactic bivalent or quadrivalent HPV vaccines, reporting serotype-specific clinical efficacy endpoints in the HPV16/18 seropositive, DNA-negative populations were included. Relative risks (RRs) of 6-month PI (6mPI), 12-month PI (12mPI), CIN1+ and CIN2+ were pooled using a random-effects model. RESULTS: A total of 1,727 citations were reviewed. 8 studies, with a total of 9,569 SPDN participants, met all eligibility criteria. The RR of 6mPI (RR=0.22; 95% confidence interval [CI]=0.08-0.61; p=0.018), 12mPI (RR=0.20; 95% CI=0.05-0.80; p=0.035), CIN1+ (RR=0.13; 95% CI=0.05-0.30; p=0.003) and CIN2+ (RR=0.15; 95% CI=0.04-0.59; p=0.022) was significantly reduced in the vaccinated compared to the unvaccinated group. CONCLUSION: Our findings suggest high serotype-specific efficacy for HPV vaccination among cohorts of women with evidence of prior HPV16/18 infections, including 87% efficacy (95% CI=70%-95%; p=0.003) against HPV16/18 cervical dysplasia. HPV vaccination is highly effective among uninfected women, regardless of prior exposure history. TRIAL REGISTRATION: PROSPERO Identifier: CRD42020206888.