Incidence of anal cancer is highest in gay and bisexual men (GBM). A better understanding of the natural history of anal high-risk human papillomavirus (HRHPV) infection is needed for anal cancer prevention.
The Study of the Prevention of Anal Cancer was a 3-year study of Australian GBM, aged 35 years or older. We examined incidence, clearance and risk factors for 13 HRHPV types tested for at baseline and 3 annual visits.
In 525 men with ≥ 2 visits, 348 (66.3%) acquired ≥ 1 incident HRHPV infection. HPV16 incidence rates were similar, but non-16 HRHPV incidence was higher in HIV-positive (51.8/100 person years, PY) than HIV-negative men (36.5/100 PY, p < 0.001). Annual clearance rates of HPV16 (13.21/100 PY, 95% CI 10.53-16.56) were lower than for other HRHPV types. HRHPV clearance rates were not associated with HIV overall but were significantly lower in those with a lower nadir CD4 (<200 cells/µl) for HPV16 (p=0.015) and other HRHPV types (p=0.007).
The higher incidence of non-16 HRHPV types, coupled with the lower clearance of non-16 HRHPV types in those with past impaired immune function, is consistent with the greater role of non-16 HRHPV in anal cancer in HIV-positive people.

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