Sections

Post-Exposure Prophylaxis (PEP)

6.1 Overview

When individuals are potentially exposed to HIV through sexual assault or occupational exposure, a programme of several antiretroviral drugs may be taken to prevent infection (post-exposure prophylaxis). PEP treatment needs to be commenced within 72 hours of the exposure, although there is evidence to suggest that the sooner the person commences treatment the greater the benefits.

Viral Load versus Risk of Transmission
Studies have shown that the primary factor increasing the chance of HIV infection is the viral load in the blood of the infected person. Other factors that can increase the chance of HIV infection include the presence of STIs and if the male is uncircumcised. On average, the chance of HIV infection per single exposure during sexual intercourse is 0.11%. However, during the acute HIV infection phase (normally 3-8 weeks after infection), and when a patient has full-blown AIDS, the viral load increases to as much as one million copies/ml, greatly increasing the risk of infection.
Viral Load Chance of transmission References
<3,500 copies/ml 0.01% chance. (1 per 10 000 episodes of intercourse) Gray, 2001
>50,000 copies/ml 0.51% chance. (5.1 per 1000 episodes of intercourse) Gray, 2001
> 1-million copies/ml* 3.00% chance. (3 per 100 episodes of intercourse) Chakraborty, 2001
* viral load in male semen. Studies have shown that the viral loads in blood and semen are comparable in the absence of STIs.
Source: Statistics adapted from: Estimating the Risk of Sexual HIV Transmission: Implications for the African Epidemic, Medscape, 2001. (Please note that in order to view this paper, you will need to register as a user of Medscape).

Why take PEP?

It is generally accepted that the average risk of a person contracting HIV from:

  • a single act of penetrative sexual intercourse is 0.1% (or 1 in a 1 000 incidences)
  • a single act of anal intercourse is 0.1%- 0.5% (or 1-5 per 1 000 incidences)
  • a needle stick injury is 0.3% (or 3 per 1 000 incidences)

However, factors such as the viral load of the infected blood, the amount of fluid involved and the nature of the injury (or sex) can affect the risk factor.

Despite the low risk of contraction through a single exposure, rape survivors and health workers do have a right to post-exposure prophylaxis.

PEP is not recommended for casual exposure to HIV/AIDS as it is not 100% effective, can have severe side effects and could encourage unsafe sexual behaviour.

Availability

PEP is theoretically available at all public sector hospitals and clinics. However, a 2004 report by Human Rights Watch found that "government failure to provide adequate information or training about PEP or clear messages in support of PEP significantly undermined access to this lifesaving service. Police, health professionals, and counselors working with rape survivors often lacked basic information about PEP, as did rape survivors themselves. As a result, many rape survivors did not get PEP simply because the various agencies charged with providing these services did not know that they existed." (Human Rights Watch, "Deadly Delay: South Africa's Efforts to Prevent HIV in Survivors of Sexual Violence")

6.2 Studies

Key Research

  1. In a 1997 study of needlestick injuries to health-care workers, "the prompt initiation of zidovudine was associated with an 81% decrease in the risk for acquiring HIV" (CDC factsheet).

  2. A 2001 study of homosexual and bisexual men who began taking PEP after a self-identified high-risk exposure found annual seroincidence (HIV-infection) was:

    • 3.9% amongst those who never used PEP
    • 1.1% amongst those who took PEP

  3. In a study of rape survivors in South Africa: Of 480 initially seronegative survivors begun on zidovudine and lamivudine and followed up for at least six weeks only one woman seroconverted (who took medication 96 hours after the assault). (CDC factsheet)

6.3 In South Africa

In South Africa, individuals who have been raped or occupationally exposed to HIV have the right to obtain treatment. Most health care workers recommend PEP treatment whether the exposure was known to be HIV-positive or not.

In 2002, the South African Cabinet resolved to make post-exposure prophylaxis available to rape survivors. In the Standard Treatment Guidelines and Essential Drugs List for South Africa (2003), recommendations are given for the use of PEP after exposure through sexual abuse and occupational injuries:

SA National Department of Health recommendations for Post-Exposure Prophylaxis

  1. Patients who have been potentially exposed to HIV 72 hours or more prior to consultation are not treated.
  2. An HIV test is compulsory. Patients who do not take an HIV test are not treated.
  3. Patients are put onto a short course of antiretrovirals during the testing phase.
  4. No PEP treatment is given to those already HIV-positive as the short treatment might lead to viral resistance.
  5. A full 28-day course of PEP is administered. Normally zidovudine (AZT) and lamivudine (3TC) are administered, but the course can include a protease inhibitor if the injury is high risk.

Adapted from: Standard Treatment Guidelines and Essential Drugs List for South Africa, 2003.