MSM represent the predominant part of the Australian population at most risk of HIV infection. The most effective way to prevent the sexual transmission of HIV and other STIs is to prevent exposure. Condom use and other behavioural methods of risk reduction, such as HIV serosorting, strategic positioning, negotiated safe practices with sexual partners and clean injecting equipment, have been used by MSM throughout the HIV epidemic to reduce the risk of HIV infection. The consistent use of condoms is the mainstay of any personal, or population level, sexual risk reduction strategy. However, the overall effectiveness of condoms in preventing HV infection during anal sex was estimated to be suboptimal at 70%[7] , mainly due to frequent condom failure (e.g. breakage, slippage, leakage, and delayed and intermittent application during sex).[8] While condom use should continue to be promoted for prevention of HIV infection and STIs, this strategy alone it is unlikely to reduce the incidence of new HIV infection.
In the last decade, there have been substantial advances in the therapeutic and preventative use of antiretroviral therapy (ART), which has assumed a cornerstone role in the current strategy for HIV prevention. Table 1 summarises various preventative uses of ART and its efficacy.
Table 1. Antiretroviral therapy as prevention
|
Prevention strategy |
Acronym |
Description |
Efficacy |
|
Postexposure prophylaxis |
PEP OPEP (occupational PEP) NPEP (non-occupational PEP) |
28 days of ART taken as soon after, and within 72 hours of, an occupational or non-occupational (sexual or injecting drug use) actual or potential HIV exposure event |
OPEP: 81% risk reduction[9] NPEP: no empirical data, strongly supported by non-human primate and prevention of mother-to-child HIV transmission studies[10] [11] |
|
Prevention of mother-to-child HIV transmission |
PMTCT |
Universal antenatal HIV screening, maternal ART, caesarean section#, short-course postnatal ART for the newborn and avoidance of breast feeding |
< 1% risk of vertical transmission (from a 13-40% risk without intervention)[12] |
|
Treatment as prevention |
TasP |
ART to men or women with HIV infection in serodiscordant relationships |
≥ 96%[13] |
|
Pre-exposure prophylaxis * |
PrEP |
Daily ART (usually coformulated tenofovir disoproxil fumarate and emtricitabine – Truvada) in HIV negative men and women |
Men who have sex with men: 44-92% [14] Heterosexual men and women: 75- 90% [15] IDU: 49 – 74%[16] |
ART: antiretroviral therapy; HIV: human immunodeficiency virus; IDU: injection drug user
# Additional benefit of caesarean section in women on antiretroviral therapy with an undetectable viral load is not established
*Maximum efficiency is dependent on high levels of adherence and detectable drug in plasma. The range represents the overall efficacy and, in those participants with detectable drug, best efficacy. The study in IDUs used tenofovir disoproxil fumarate alone.
The following information focuses on the latest developments in HIV prevention and how clinicians, mainly general practitioners and nurses, can contribute to the assessment and care of HIV-negative men and women using antiretroviral drugs for HIV prevention. Four preventative methods will be reviewed, specifically treatment as prevention (TasP), non-occupational post-exposure prophylaxis (NPEP), pre-exposure prophylaxis (PrEP) and topical microbicides containing antiretroviral drugs.