OBJECTIVE: Anal cancer precursor lesions high-grade anal intraepithelial neoplasia (HGAIN) are highly prevalent among HIV+ MSM. Treatment of HGAIN is frustrated by high recurrence rates. We investigated the efficacy of the quadrivalent human papillomavirus (qHPV) vaccine as posttreatment adjuvant in preventing HGAIN recurrence in HIV+ MSM. DESIGN: Randomized, double-blind, placebo-controlled, multicentre trial. SETTING: Three HIV outpatient clinics in Amsterdam, the Netherlands. SUBJECTS: HIV+ MSM with CD4+ cell count more than 350 cells/μl, biopsy-proven intra-anal HGAIN successfully treated in the past year, and lesions still in remission at enrolment, as assessed by high-resolution anoscopy (HRA). INTERVENTION: Participants were randomized to three doses of qHPV (Gardasil-4, MSD) or placebo with vaccinations at 0, 2, and 6 months. HRA was repeated at 6, 12, and 18 months. MAIN OUTCOME MEASURE: The primary outcome was cumulative, biopsy-proven HGAIN recurrence rate at 18 months, evaluated in an intention-to-treat (ITT) (received all vaccinations) and per-protocol analysis (all vaccinations and complete follow-up). RESULTS: We randomized 126 participants of which 64 (50.8%) received qHPV and 62 (49.2%) placebo. All participants received three vaccinations, and in both groups for two participants follow-up was incomplete. We found no difference (P = 0.38) in cumulative HGAIN recurrence rates between the qHPV (44/64, 68.8%) and placebo group (38/62, 61.3%) in the ITT analysis [absolute risk reduction -7.5 (95% confidence interval (CI) -24.1 to 9.2)]. This was similar in the per-protocol analysis. CONCLUSION: Despite adequate serological responses to qHPV vaccination, short-term recurrence of HGAIN was not prevented. These findings do not support qHPV vaccination as a treatment adjuvant to prevent HGAIN recurrence in HIV+ MSM.