Impact of Human Papillomavirus Vaccine Against Anal Human Papillomavirus Infection, Anal Intraepithelial Neoplasia, and Recurrence of Anal Intraepithelial Neoplasia: A Systematic Review and Meta-analysis.

BACKGROUND: We sought to summarize human papillomavirus (HPV) vaccine efficacy/effectiveness (VE) against anal HPV infection and anal intraepithelial neoplasia (AIN). METHODS: We performed literature review and meta-analysis to estimate VE, stratified by age and analytic population (per-protocol efficacy [PPE] or intention-to-treat [ITT] population in clinical trials, or all participants in real-world studies). RESULTS: We identified 6 clinical trials and 8 real-world studies. In participants vaccinated at age ≤26 years (mainly human immunodeficiency virus [HIV]-negative individuals), significant VE against incident/prevalent anal HPV infection was reported in clinical trials, with a higher estimate in PPE (2 studies with 2390 participants; VE, 84% [95% confidence interval (CI), 77%-90%]; I2 = 0%) than ITT (2 studies with 4885 participants; 55%, 39%-67%; I2 = 46%) populations or in real-world studies (4 studies with 2375 participants; 77%, 40%-91%; I2 = 81%). HPV vaccination at age ≤26 years was associated with significant VE in preventing persistent anal HPV infection and AIN. No significant VE against anal HPV infection or AIN was found in persons vaccinated at age >26 years (mainly people living with HIV). CONCLUSIONS: There is strong evidence for high VE against anal HPV infection and AIN in HIV-negative individuals vaccinated at age ≤26 years. However, the lower impact in ITT than in PPE populations and the lack of significant effect in people living with HIV aged >26 years indicates that vaccines have the higher impact in populations with less sexual exposure to anal HPV.