HIV This Week

http://www.bmj.com/cgi/reprint/335/7613/248

Photo credit: UNAIDS -Y. Shuimizu

A systematic review was conducted to assess the effects of sexual abstinence-only programmes for HIV prevention among participants in high-income countries. Data sources were 30 electronic databases without linguistic or geographical restrictions to February 2007, contacts with experts, hand searching, and cross referencing. Two reviewers independently applied inclusion criteria and extracted data, resolving disagreements by consensus and referral to a third reviewer. Randomised and quasi-randomised controlled trials of abstinence-only programmes in any high-income country were included. Programmes aimed to prevent HIV only or both pregnancy and HIV. Trials evaluated biological outcomes (incidence of HIV, sexually transmitted infection, pregnancy) or behavioural outcomes (incidence or frequency of unprotected vaginal, anal, or oral sex; incidence or frequency of any vaginal, anal, or oral sex; number of partners; condom use; sexual initiation). The search identified 13 trials enrolling about 15,940 US youths. All outcomes were self-reported. Compared with various controls, no programme affected incidence of unprotected vaginal sex, number of partners, condom use, or sexual initiation. One trial observed adverse effects at short-term follow-up (sexually transmitted infections, frequency of sex) and long-term follow-up (sexually transmitted infections, pregnancy) compared with usual care, but findings were offset by trials with non-significant results. Another trial observed a protective effect on incidence of vaginal sex compared with usual care, but this was limited to short-term follow-up and countered by trials with non-significant findings. Heterogeneity prevented meta-analysis. Programmes that exclusively encourage abstinence from sex do not seem to affect the risk of HIV infection in high-income countries, as measured by self-reported biological and behavioural outcomes.

Editors’ note: This methodologically rigourous search found only 13 randomised controlled trials, all in the United States. Programmes presenting abstinence as the exclusive option for HIV prevention were compared with control arms which received either no intervention, a different intervention, or a time delayed exposure to the intervention. Confirming the findings of previous reviews, it found that abstinence-only programmes for HIV prevention basically have no effect – they neither decrease nor increase sexual risk among young people in high-income countries. Although these findings cannot be generalized to low- and middle-income settings or to other high-income settings, they do give pause for reflection, given the amounts of resources being devoted to such unproven programmes.

The majority of human immunodeficiency virus (HIV) infections in the world are sexually transmitted and quantities of HIV in genital fluids are an important transmission risk-determining factor. Estimating men's sexual HIV infectiousness from blood viral load hinges on the association between HIV in blood plasma and semen. This article reviews research on the association between blood plasma viral load and semen viral load as reported in 19 empirical studies (N = 1226). Findings yielded a mean correlation between blood plasma viral load and semen viral load of 0.45 (SD = 0.20, median = 0.45, range = 0.07-.64). Semen viral load was generally lower than blood plasma viral load, but this pattern was variable across studies. Co-occurring sexually transmitted infections (urethritis), nonsuppressive HIV treatments, and drug resistance account for the variability in observed correlations. HIV disease progression does not reliably influence the association between blood plasma viral load and semen viral load. Research is needed to determine the degree to which blood plasma viral load as well as semen viral load predict HIV transmission. 

Editors’ note: This review highlights how much we know and what more we need to know. Because an undetectable viral load significantly reduces the risk of HIV sexual transmission, serodiscordant couples desiring a pregnancy are advised to achieve consistent undetectable viral loads prior to attempting conception. As noted previously, for additional protection some are even using pre-exposure prophylaxis for the uninfected partner, in the absence of evidence that it is safe or adds benefit. Information on the associations between viral load in blood and viral load in semen or vaginal secretions, related probabilities of HIV transmission, and the differential concentration of antiretroviral drugs in genital secretions is emerging and will help inform individual decision-making about risk as well as drug choices for inclusion in second generation vaginal and rectal microbicides.

The aim of the study was to describe the use of nonoccupational postexposure prophylaxis (N-PEP) in Australia, and to estimate the number of HIV infections that its use prevented. Poynten and colleagues conducted a population-based observational cohort study of people who presented to antiretroviral prescribers in Eastern Australia, and reported a high-risk nonoccupational exposure to HIV, in 1998-2004. Prescribers collected data at baseline, 4 weeks, and 6 months. Data collected included details of HIV exposure, drug regimens, and HIV serostatus. The great majority of the 1601 participants were male (95%) and presented after male homosexual exposure (87%). Only 32% of exposures were to HIV-positive sources. Two antiretroviral drugs were prescribed after 48% of events and three or more drugs after 52% of events. The median time to receipt of NPEP was 23 h. Side effects were reported by 66% of participants. No case of N-PEP failure in an adherent individual was identified. It was estimated that 0.9-9.2 HIV infections had been prevented. This compared with a total of 1138 newly acquired HIV infections notified in the geographical area covered by the study. In Australia, N-PEP has been widely prescribed and is mainly targeted at high-risk exposures. Although there were no identified failures of N-PEP, it is likely that only a small proportion of new HIV infections in the study area were prevented. N-PEP may be a valuable preventive intervention for an individual, but it can only play a minor role in HIV prevention at the population level unless targeting can be further improved.

Editors’ note: The costs and opportunity costs of devoting resources to antiretroviral post-exposure prophylaxis for a non-occupational exposure will vary by socio-economic and epidemic setting. No randomised controlled trials of N-PEP have been conducted but it is assumed that it would work on the same principle as prevention of mother-to-child transmission. Hospital emergency rooms and rape crisis centres should have starter packs for unanticipated HIV exposure, but highest priority should be given to primary prevention of HIV exposure in the first place.