HPV vaccine effectiveness against prevalent HPV by age, years sexually active before vaccination, and HIV status in gay, bisexual, and other men who have sex with men, 2019-2021.

BACKGROUND: We compared the prevalence of vaccine-preventable anal human papillomavirus (HPV) types among gay, bisexual, and other men who have sex with men (GBM) living in large cities in Canada from 2019 to 2021 by age and HIV status. METHODS: Sexually-active GBM ≥16 years were recruited in Montreal, Toronto, and Vancouver using respondent-driven sampling (RDS). Participants self-reported HPV vaccination and self-collected anal HPV specimens. We estimated the prevalence of vaccine-preventable types for participants during the 2019 to 2021 period. We report RDS-II-weighted prevalence and confounder-adjusted prevalence ratios (aPRs) comparing vaccinated (≥1 dose) and unvaccinated GBM using multivariable Poisson regression. RESULTS: Among 1,159 participants aged 18-83 (median 35 years), 17.6% were living with HIV, and 62.2%, 40.2% and 15.0% were vaccinated in the 16-26, 27-45, and ≥46-year groups, respectively. Among GBM 16-26 years, HPV6/11/16/18 prevalence was lower among those vaccinated ≤23 years (aPR= 0.40, 95% CI: 0.20-0.77), ≥3 years since first dose (aPR=0.39; 95% CI: 0.18-0.85), and those with ≤5 years of sexual activity before vaccination (aPR=0.47; 95%CI: 0.25-0.89). HPV6/11/16/18/31/33/45/52/58 prevalence was lower among those vaccinated ≤26 years in GBM aged 27-45 years (aPR= 0.81, 95% CI, 0.61-1.08), though this did not reach statistical significance. CONCLUSIONS: Five years after implementation of Canadian HPV vaccination programs for younger GBM, anal HPV prevalence was lower among those vaccinated at younger ages and near sexual debut.