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Can unsafe sex be safe? Review of sexual transmissibility of HIV-1 according to viral load, HAART, and sexually transmitted infections

Presented by Suzanna Attia, Switzerland.

S. Attia1, M. Egger1, N. Low1

1University of Bern, Institute of Social and Preventive Medicine, Bern, Switzerland

Background: Controversy exists over a Swiss Federal Commission’s statement that the risk per sex act of HIV-1 transmission from an individual on antiretroviral therapy with completely suppressed viremia and without another sexually transmitted infection is <1:100,000. Our goal was to review evidence about this issue systematically, to estimate HIV-1 sexual transmission rates, and to quantify uncertainty using confidence intervals.
Methods: We searched for prospective cohort studies of serodiscordant couples within Medline and Embase from 1996 onwards, citations from resulting articles, and abstracts from all IAS Conferences and Conferences on Retroviruses and Opportunistic Infections. We selected studies, assessed study quality, and extracted data in duplicate. We asked authors for additional information in order to stratify transmission events by viral load, use of HAART, and the presence of other sexually transmitted infections. We will present this information in a meta-analysis of HIV-1 transmission rates.
Results: We included 15 cohorts identified from 165 published articles and 93 abstracts reporting on 5161 heterosexual serodiscordant couples, amongst whom 433 HIV-infected partners were on HAART. Nine of these cohorts were reported as abstracts only. Follow-up times and viral load categories were reported inconsistently. In four papers and one abstract with a total of 1587 untreated HIV-positive partners, no transmissions were reported from those individuals with <1000 copies/ml blood viral load.
Conclusions: The suggested <1:100,000 risk per sex act of HIV transmission by a HAART-treated HIV-1 positive individual with suppressed viremia could neither be confirmed nor excluded from the limited published data. The influence of other sexually transmitted infections remains unclear. This meta-analysis and an ongoing multi-centre randomized trial will provide more precise data about HIV transmission risk under HAART. At present, the negative impact of a public message that has been interpreted as promoting unprotected sex might outweigh the potential benefit to the intended recipients.

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