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Background. Most squamous cell anal cancers and precancerous lesions are attributed to human papillomavirus (HPV) infection. By preventing HPV infection, quadrivalent HPV vaccine (qHPV) reduces risk of anal cancer/precancerous lesions in young men who have sex with men (MSM) without history of anal cancer/precancerous lesions. In our practice, many persons with history of precancerous anal lesions or high-grade anal intraepithelial neoplasia (HGAIN) have been vaccinated electively. We determined whether qHPV is effective at preventing recurrence of HGAIN.Methods. This nonconcurrent cohort study evaluated 202 patients with a history of previously treated HGAIN. Eighty-eight patients were vaccinated, and 114 patients were unvaccinated. We determined the recurrence rate of histologic HGAIN in vaccinated versus unvaccinated patients.Results. During 340.4 person-years follow-up, 12 (13.6%) vaccinated patients and 35 (30.7%) unvaccinated patients developed recurrent HGAIN. Multivariable hazards ratio (HR) analysis showed testing positive for oncogenic HPV genotypes within 8 months before study entry was associated with increased risk of recurrent HGAIN at 2 years after study entry (HR 4.06; 95% confidence interval [CI], 1.58–10.40; P = .004), and qHPV was associated with decreased risk of recurrent HGAIN (HR .50; 95% CI, .26–.98; P = .04). Among patients infected with oncogenic HPV, qHPV was associated with decreased risk of recurrent HGAIN at 2 years after study entry (HR .47; 95% CI, .22–1.00; P = .05).Conclusions. qHPV significantly reduces HGAIN recurrence among MSM and may be an effective posttreatment adjuvant form of therapy. A randomized controlled trial is needed to confirm these results.