Initially HIV-negative men who have sex with men (MSM) who recently took postexposure prophylaxis (PEP) against HIV had a significantly higher subsequent HIV incidence than initially negative MSM in the Amsterdam Cohort Study, according to results of a 10-year study. The difference in HIV incidence between the two groups became more marked in recent years.

HIV-negative people exposed to HIV in developed countries can often receive PEP to protect themselves from chronic HIV infection. Because little is known about sexual behavior after PEP among MSM, researchers in Amsterdam planned this analysis.

The study involved 395 MSM recently prescribed PEP after HIV exposure from 2000 through 2009. All men had a follow-up visit with an HIV test 3 and/or 6 months after being prescribed PEP. The comparison group consisted of 782 HIV-negative men in the Amsterdam Cohort Study who were not prescribed PEP.

From 2000 through 2009 overall HIV incidence (the new infection rate) stood at 6.4 per 100 person-years (95% confidence interval [CI] 3.4 to 11.2) in the PEP group and 1.6 (95% CI 1.3 to 2.1) in the Amsterdam Cohort Study group, a significant difference (P < 0.01).

Over time, HIV incidence rose in the PEP group (incidence rate ratio [IRR] 1.3, 95% CI 0.9 to 1.7) and in the cohort group (IRR 1.1, 95% CI 1.0 to 1.2). Compared with the cohort group, the PEP group had nearly a 5 times higher HIV incidence in 2009 (IRR PEP-vs-Cohort 4.8, 95% CI 2.0 to 11.5).

“Particularly in more recent years,” the researchers conclude, “MSM recently prescribed PEP had a higher HIV incidence compared with MSM participating in the Amsterdam Cohort Study, indicating ongoing sexual risk behaviour.”

Source: José Heuker, Gerard J.B. Sonder, Ineke Stolte, Ronald Geskus, Anneke van den Hoek. High HIV incidence among MSM prescribed postexposure prophylaxis, 2000–2009: indications for ongoing sexual risk behavior. AIDS.. 2012; 26: 505-512.

By Mark Mascolini

For the study abstract