Preventing HIV

Strategies to help prevent the transmission of HIV include treatment as prevention, pre- and post-exposure prophylaxis. The evidence for each approach is provided here.


Evidence for the efficacy of antiretroviral therapy (ART) in preventing HIV transmission has generated optimism and been hailed as a turning point in stopping the HIV epidemic.1 The role of ART in prevention can be summarised as follows:

  • Treatment as prevention (TasP): Achieving viral suppression using effective ART in people living with HIV (PLHIV) in order to reduce the risk of HIV transmission.
  • Post-exposure prophylaxis (PEP): Reducing the risk of infection in HIV-negative individuals with a recent possible exposure to HIV.
  • Pre-exposure prophylaxis (PrEP): Reducing the risk of infection in HIV-negative individuals at high risk of acquiring HIV.

Treatment as prevention

Several studies have demonstrated that the risk for sexual transmission is markedly reduced in PLHIV taking ART with low plasma HIV-1 RNA.2, 3

The landmark HPTN 052 study compared the effects of early versus delayed ART on the sexual transmission of HIV in serodiscordant couples.2 Early ART demonstrated durable benefit for reducing HIV transmission (93% risk reduction over the 10-year period). No linked partner infections occurred while the partner with HIV had an undetectable viral load during ART. Similarly, in the observational PARTNER study of HIV-serodifferent couples (heterosexual and men who have sex with men), there we no cases of within-couple HIV transmission where one partner was HIV positive but on suppressive ART.3 As a result, international guidelines now recommend that ART should be offered to all PLHIV, irrespective of CD4+ cell count, to reduce risk of transmission.4

Post-exposure prophylaxis (PEP)

Guidelines issued by the European AIDS Clinical Society (EACS) recommend PEP for cases of exposure to HIV through:4


  • Subcutaneous or intramuscular penetration with a surgical needle or intravascular device exposed to blood from a HIV-positive person or a person with unknown serostatus with HIV risk factors.
  • Percutaneous injury with a sharp instrument (e.g. lancet), subcutaneous or intramuscular needle/suture needle, from a HIV-positive person.
  • Contact for more than 15 minutes with mucous membrane or non-intact skin belonging to a HIV-positive person.

Genital secretions

  • Anal or vaginal sex, if the partner is HIV-positive or serostatus is unknown but HIV risk factors are present. If the partner is HIV-positive but on ART, PEP should be started. HIV viral load should be repeated and if the HIV-positive partner is undetectable, PEP can be stopped.
  • Receptive oral sex with ejaculation if the sexual partner is HIV-positive and has viraemia.

Intravenous drug use

  • Exchange of syringes, needles or other preparation material with a HIV-positive person.

Pre-exposure prophylaxis (PrEP)

When taken consistently, PrEP has been shown to reduce the risk of HIV infection in people who are at high risk by up to 92%.5 However, PrEP does not protect against other sexually-transmitted infections and therefore, should be used in combination with other preventive interventions.4

The only medication regimen approved by the European Medicines Agency and recommended for PrEP to reduce the risk of sexually acquired HIV-1 infection in adults and adolescents at high risk is daily tenofovir (TDF) 300 mg co-formulated with emtricitabine (FTC) 200 mg (Truvada®).6

The EACS Guidelines recommend PrEP for the following cohorts:4

  • Adults who are at high risk of acquiring HIV infection when condoms are not used consistently.
  • HIV-negative men who have sex with men and transgender individuals who do not consistently use condoms.
  • HIV-positive partners who are not taking ART.
  • HIV-negative heterosexual men and women who have multiple sexual partners – some of whom are likely to have HIV infection and not be on treatment – and aren’t consistent with condom use.