Prevention

Sexual contact

Consistent condom use reduces the risk of HIV transmission by approximately 80% over the long term. When one partner of a couple is infected, consistent condom use results in rates of HIV infection for the uninfected person of below 1% per year. There is some evidence to suggest that female condoms may provide an equivalent level of protection. Application of a vaginal gel containingtenofovir (a reverse transcriptase inhibitor) immediately before sex seems to reduce infection rates by approximately 40% among African women. By contrast, use of the spermicide nonoxynol-9 may increase the risk of transmission due to its tendency to cause vaginal and rectal irritation. Circumcision in Sub-Saharan Africa "reduces the acquisition of HIV by heterosexual men by between 38% and 66% over 24 months". Based on these studies, the World Health Organization and UNAIDS both recommended male circumcision as a method of preventing female-to-male HIV transmission in 2007. Whether it protects against male-to-female transmission is disputed and whether it is of benefit in developed countries and among men who have sex with men is undetermined. Some experts fear that a lower perception of vulnerability among circumcised men may result in more sexual risk-taking behavior, thus negating its preventive effects. Women who have undergone female genital cutting have an increased risk of HIV. Programs encouraging sexual abstinence do not appear to affect subsequent HIV risk. Evidence for a benefit from peer education is equally poor. Comprehensive sexual education provided at school may decrease high risk behavior. A substantial minority of young people continues to engage in high-risk practices despite knowing about HIV/AIDS, underestimating their own risk of becoming infected with HIV. It is not known if treating other sexually transmitted infections is effective in preventing HIV.

Pre-exposure

Treating people with HIV whose CD4 count ≥ 350cells/µL with antiretrovirals protects 96% of their partners from infection. Pre-exposure prophylaxis with a daily dose of the medications tenofovir, with or without emtricitabine, is effective in a number of groups including: men who have sex with men, couples where one is HIV positive, and young heterosexuals in Africa.

Universal precautions within the health care environment are believed to be effective in decreasing the risk of HIV. Intravenous drug use is an important risk factor and harm reduction strategies such as needle-exchange programmes and opioid substitution therapy appear effective in decreasing this risk.

Post-exposure

A course of antiretrovirals administered within 48 to 72 hours after exposure to HIV positive blood or genital secretions is referred to as post-exposure prophylaxis. The use of the single agent zidovudine reduces the risk of subsequent HIV infection fivefold following a needle stick injury. Treatment is recommended after sexual assault when the perpetrator is known to be HIV positive but is controversial when their HIV status is unknown. Current treatment regimes typically use lopinavir/ritonavir and lamivudine/zidovudine oremtricitabine/tenofovir and may decrease the risk further. The duration of treatment is usually four weeks and is frequently associated with adverse effects (with zidovudine in about 70% of cases, including nausea in 24%, fatigue in 22%, emotional distress in 13%, and headaches in 9%).

Mother-to-child

Programs to prevent the vertical transmission of HIV (from mothers to children) can reduce rates of transmission by 92–99%. This primarily involves the use of a combination of antiviral medications during pregnancy and after birth in the infant and potentially includes bottle feeding rather than breastfeeding. If replacement feeding is acceptable, feasible, affordable, sustainable, and safe, mothers should avoid breastfeeding their infants; however exclusive breastfeeding is recommended during the first months of life if this is not the case. If exclusive breastfeeding is carried out, the provision of extended antiretroviral prophylaxis to the infant decreases the risk of transmission.

Vaccination

As of 2012 there is no effective vaccine for HIV or AIDS. A single trial of the vaccine RV 144 published in 2009 found a partial reduction in the risk of transmission of roughly 30%, stimulating some hope in the research community of developing a truly effective vaccine. Further trials of the RV 144 vaccine are ongoing.

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