HIV transmission risk through anal intercourse: systematic review, meta-analysis and implications for HIV prevention

Rebecca Frances Baggaley (1) , Richard G White (2) , Marie-Claude Boily (3)

1 Infectious Disease Epidemiology
2 EPH
3 Infectious Disease Epidemiology

Background: The HIV infectiousness of anal intercourse (AI) has not been systematically reviewed, despite its role driving HIV epidemics among men who have sex with men (MSM) and its potential contribution to heterosexual spread. We assessed the per-act and per-partner HIV transmission risk from AI exposure for heterosexuals and MSM and its implications for HIV prevention. Methods: Systematic review and meta-analysis of the literature on HIV-1 infectiousness through AI was conducted. PubMed was searched to September 2008. A binomial model explored the individual risk of HIV infection with and without HAART. Results: 62,643 titles were searched; four publications reporting per-act and 12 reporting per-partner transmission estimates were included. Overall, random effects model summary estimates were 1.4% (95%CI 0.2-2.5) and 40.4% (95%CI 6.0-74.9) for per-act and per-partner unprotected receptive AI (URAI), respectively. There was no significant difference between per-act risks of URAI for heterosexuals and MSM. Per-partner unprotected insertive AI (UIAI) and combined URAI-UIAI risk were 21.7% (95%CI 0.2-43.3) and 39.9% (95%CI 22.5-57.4) respectively, with no available per-act estimates. Per-partner combined URAI-UIAI summary estimates, which adjusted for additional exposures other than AI with a "main" partner (7.9% [95%CI 1.2-14.5]), were lower than crude (unadjusted) estimates (48.1% [95%CI 35.3-60.8]). Our modelling demonstrated that it would require unreasonably low numbers of AI HIV exposures per partnership to reconcile the summary per-act and per-partner estimates, suggesting considerable variability in AI infectiousness between and within partnerships over time. AI may substantially increase HIV transmission risk even if the infected partner is receiving HAART; however predictions are highly sensitive to infectiousness assumptions based on viral load. Conclusions: Unprotected AI is a high risk practice for HIV transmission, probably with substantial variation in infectiousness. The significant heterogeneity between infectiousness estimates means that pooled AI HIV transmission probabilities should be used with caution. Recent reported rises in AI amongst heterosexuals suggests a greater understanding of the role AI plays in heterosexual sex lives may be increasingly important for HIV prevention.

Mots clés: Medicine

Rebecca Frances Baggaley, Richard G White, Marie-Claude Boily. HIV transmission risk through anal intercourse: systematic review, meta-analysis and implications for HIV prevention. International Journal of Epidemiology, 2010, ⟨10.1093/ije/DYQ057⟩. ⟨hal-00587268⟩