The most widely available tool for prevention of HIV infection during sexual intercourse is the male condom. Male condoms afford a high degree of protection: consistent and correct male condom use reduces HIV transmission by 80% to 97%. Numerous studies have shown that the female condom is an acceptable method for many women and men, and is a valuable alternative for women whose partners refuse to use male condoms. Unlike the male condom, the female condom can be inserted some time before sex, and does not depend on the same degree of male co-operation for its successful use.
Pre-exposure prophylaxis (PrEP)
Studies have shown the effectiveness of daily oral antiretroviral therapy (ART), known as PrEP, in reducing the risk of HIV infection in adults who are at high risk for HIV acquisition. [ ] Evidence shows that oral tenofovir and emtricitabine prophylaxis is highly effective in reducing the risk of HIV acquisition and is considered safe, with minimal adverse effects. There are also data that provide reassurance that resistance is unlikely to occur in patients taking PrEP. As a consequence, it is increasingly being incorporated into international guidelines.
World Health Organization guidelines strongly recommend offering PrEP containing tenofovir to HIV-negative individuals who are at substantial risk of HIV infection as part of combination prevention approaches.
The US Preventive Services Task Force also recommends PrEP (with tenofovir alone or tenofovir plus emtricitabine) in high-risk people, including: sexually active MSM who have a serodiscordant partner, inconsistently use condoms, or have had gonorrhoea, chlamydia, or syphilis in the past 6 months; sexually-active heterosexual people who have a serodiscordant partner, inconsistently use condoms with a high-risk partner whose HIV status is unknown, or have had gonorrhoea or syphilis recently; and people who inject drugs and either share equipment or who are at risk of sexual acquisition.
The US Centers for Disease Control and Prevention recommends PrEP with tenofovir and emtricitabine as one prevention option for: adult sexually-active men who have sex with men (MSM) who are at substantial risk for HIV acquisition; adult heterosexually active men and women at substantial risk for HIV acquisition; and adult injection drug users at substantial risk for HIV acquisition. Furthermore, PrEP should be discussed with adult heterosexually active men and women whose partners are known to be infected with HIV (serodiscordant couples).
However, it should be noted that there has been a case report of tenofovir-susceptible, emtricitabine-resistant HIV acquisition despite high adherence to PrEP. New treatments for PrEP are currently in development. Emtricitabine and tenofovir (as either the alafenamide or disoproxil fumarate salts) are available in a combination formulations specifically approved for PrEP.
Pericoital (on-demand) PrEP may be considered instead of daily PrEP in MSM who have infrequent sexual exposures. On-demand PrEP has been found to be effective in MSM who are at a high risk of HIV infection. However, a post-hoc analysis of the ANRS IPERGAY trial found that on-demand PrEP was also effective in MSM who were at a lower risk of HIV infection (i.e., periods of less frequent sexual intercourse defined as 5 episodes per month), with a 100% relative reduction of HIV incidence reported compared with placebo. In Australia, use of PrEP has been associated with a rapid decline in new HIV infections among MSM. However, a rapid increase in the use of PrEP by MSM also resulted in an equally rapid decrease in consistent condom use. Use of PrEP has increased in MSM from 6% in 2014 to 35% in 2017. Use increased in almost all demographic subgroups, but remains lower among black and Hispanic MSM.
Treatment as prevention
ART may be used to prevent HIV transmission. This is commonly known as undetectable=untransmittable (or U=U). Several large studies have shown that ART prevents HIV transmission in both heterosexual couples and MSM who maintain an undetectable viral load. In light of this evidence, US guidelines recommend that physicians should inform patients that maintaining a HIV RNA level <200 copies/mL with ART prevents transmission to sexual partners. Another form of prevention should be used for the first 6 months of ART until an HIV RNA level of <200 copies/mL has been documented, with some experts recommending that sustained suppression is confirmed before assuming there is no risk of transmission. The Prevention Access Campaign has also released a consensus statement stating that the risk of HIV transmission from a person living with HIV who is on ART and has achieved undetectable viral load in their blood for at least 6 months is negligible to non-existent. Prevention Access Campaign: consensus statement external link opens in a new window Immediate initiation of ART is recommended for the HIV-positive partner of HIV-serodiscordant couples, to prevent HIV transmission. [ ]
The role of male circumcision in the prevention of HIV and STI acquisition has been shown in a number of cross-sectional studies and randomised controlled trials from different parts of Africa, with evidence suggesting reduction in HIV acquisition in circumcised men. [ ]
Other harm reduction methods
Convincing evidence exists for the benefit of needle exchange and clean syringes in the setting of methadone clinics, termed 'harm reduction', where HIV transmission risk is related to shared intravenous drug use equipment. In addition, the supply of HIV-free blood and blood products, as well as sterile needles and syringes for injections and universal precautions in hospitals, has much reduced nosocomial transmission of HIV.
Despite a great amount of research and clinical trials, an effective vaccine for the prevention and control of HIV has yet to be discovered. Long-acting injectable PrEP is undergoing clinical trials and may address issues with adherence, and could be an important prevention intervention for certain HIV populations.
Sexual contacts of the patient should be enquired about. HIV status may already be known. If not, disclosure should be discussed. Patients may not be able to do this immediately but should be encouraged, especially in a situation where disclosure is linked to being able to practice safer sex. Practitioners may also offer to assist with disclosure under these circumstances and offer immediate testing for partners. There may be local regulations, and physicians should refer to these where appropriate. Public health officers may be able to facilitate partner notification.
Serodiscordant partners should be encouraged to be tested regularly, and can be protected from infection by immediate initiation of antiretroviral therapy in the HIV-positive partner. [ ] Tenofovir-based microbicide gel has reduced rates of HIV transmission to women.
The physician should enquire whether the patient has children and how old they are. Their well-being and medical histories may give a clue to possible infection (if not already tested). If younger than 10 years of age and well and not previously tested, the physician may also advise having them tested. Children younger than 18 months of age may need a nucleic acid test (qualitative polymerase chain reaction). If still breastfeeding, advice against on-going transmission risk should be given and consideration to weaning (if older than 6 months of age) or switching to bottle/formula feeding.
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