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HIV Post-Exposure Prophylaxis

Post-Exposure Prophylaxis (PEP) is the administration of short-term antiretroviral therapy (ART) to HIV-negative people who may have been occupationally or sexually exposed to HIV. Once exposed to HIV, there may be a brief period before the infection is established, during which ART may successfully prevent viral replication.

Every presentation for PEP should be assessed on a case-by-case basis, balancing the potential harms and benefits of treatment. In most circumstances, these presentations should be discussed with the Infectious Diseases on-call to inform whether or not PEP should be prescribed. Advice may be sought from the local Sexual Health clinic, particularly for information regarding local PEP policies. Contact details of the closest appropriate Sexual Health Service are available here. For further sexual health information/advice, patients and clinicians can also contact the NSW Sexual Health Infolink on 1800 451 624, or visit the Sexual Health Infolink website.

Assessment of risk


*What is the HIV transmission risk/exposure?

All sexual risk estimations are for unprotected sexual contact. It is assumed that a similar risk is incurred when a condom fails. See Table 1 in the ASHM Guidelines.

# What is the HIV status of the source individual?

In cases where the source refuses to disclose their HIV status or have an HIV test, it should be assumed (for the purposes of PEP prescription) that they are HIV positive. If the source cannot be contacted, the seroprevalence data will assist in determining the need for PEP. See Table 2 in the ASHM guidelines.

Clinical assessment

1. Details of the exposure (when, with whom, what, and where):

  • time of exposure

  • details of source

  • exact mode and details of exposure (including contributory factors) blood or body fluid involved, trauma, first aid measures applied

  • place of exposure

2. Information about the exposed person:

  • most recent HIV test and resulta

  • potential exposures within the last 3 months (and earlier as indicated)

  • previous post-exposure prophylaxis and history of this treatment

  • evaluation of current STIs; hepatitis B and C infection

  • pregnancy risk, contraception and lactation, consider emergency contraception

  • medical history, all medications and drug allergies

  • psychiatric history

  • drug and alcohol history

  • their knowledge of the source (if unavailable for interview)

a PEP is intended for HIV-negative individuals only. The possibility that the exposed individual has pre-existing HIV infection should always be explored as part of the process of assessing eligibility.

3. Information about the source:

  • HIV status and other relevant demographic features

  • if HIV positive:

(i) plasma viral load and CD4

(ii) antiretroviral treatment history (has resistance been an issue, if so with which drugs?)

(iii) recent HIV resistance genotyping

  • current or past STIs; hepatitis B and C status

4. The time of the assessment and first dose, if prescribed

Baseline testing

Baseline testing for:

  • HIV antibody

  • Hepatitis B serology

  • Hepatitis C serology

  • STI screena


  • pregnancy testb

a for patients presenting after non-occupational exposure

bfor all women of reproductive age

Further HIV antibody testing occurs at 4 to 6 weeks and 3 months after exposure. The decision to conduct other follow-up testing is dependent on mode of exposure and other factors.

Prescribing PEP

PEP should be prescribed as soon as possible after the exposure and within 72 hours. Patients must be informed about the uncertain efficacy of PEP, importance of adherence and potential adverse effects and drug interactions associated with antiretrovirals. Antiretroviral medication given to HIV-negative people reduces likelihood of HIV seroconversion by approximately 80%.

1. Time to initiation

Early initiation of PEP, as soon as possible after exposure, is strongly urged. PEP should NOT be offered more than 72 hours after exposure.

2. Duration of treatment

A 28-day course of PEP is recommended. Adherence to a full 28-day course of ART is critical to the effectiveness of the intervention.

3. Drugs

There is no direct evidence to support the greater or lesser efficacy of 3 over 2 drug preventive regimens. The recommendation for the number of antiretroviral drugs is based on an extrapolation of the possible benefit conferred by increased numbers/classes of drugs for HIV treatment. See Table 4 in the ASHM guidelines.

Most NSW emergency departments have access to PEP starter packs: these encourage follow-up, support adherence and minimise drug waste if the course is not finished. Co-formulated preparations reduce pill burden and improve adherence. Specific drugs contained within these packs are variable.

Factors to consider include the presence of co-morbidities, simplicity of the dosing regimen, minimisation of side effects and drug interactions. Side effects of drugs used in PEP include nausea, vomiting, diarrhoea, abdominal pain, or headache.

4. Follow up

Individuals presenting for consideration of PEP should have a plan made for delivery of results and follow up. Where possible, this should occur at local Sexual Health or Community Health Services.

Management of possible exposure to other conditions

1. Hepatitis B

All individuals presenting for PEP are assessed for the possibility of hepatitis B exposure. Individuals with evidence of previous immunity to hepatitis B (HBsAb positive) will require no further follow-up. Non-immune individuals require immunisation and follow-up (to 6 months). If the individual is non-immune and the source is known to have chronic hepatitis B (HBsAg positive), then a single dose of HBIG should be administered along with subsequent immunisation and follow-up (to 6 months).

2. Sexually transmissible infections

Individuals presenting for non-occupational post-exposure prophylaxis are screened for chlamydia, gonorrhoea and syphilis as indicated by the exposure, local epidemiology and guidelines.

3. Hepatitis C

Individuals who are potentially at risk of hepatitis C infection after exposure require follow-up for this and specialist referral if seroconversion is detected. They should be informed of symptoms of acute hepatitis, with advice to present if these occur.

4. Pregnancy

All women who have the potential to be pregnant on presentation for PEP should be offered pregnancy testing. Emergency contraception is offered to women presenting for PEP who are at risk of pregnancy. Follow-up pregnancy tests should be offered at two weeks post-exposure where indicated. Specialist advice should be sought urgently for women who require PEP and are pregnant or breastfeeding.

5. Tetanus

Individuals who sustain wounds or abrasions should have their tetanus status assessed and be offered immunisation as indicated.

Other management

Patients should be advised to adopt preventive practices until their seronegative status is confirmed at follow-up. This applies to safe sexual and injecting behaviour as well as preventing exposing others to their body fluids through other means such as accidents or body tissue donation. Women should be counselled about pregnancy, the risk of mother-to-child transmission and contraception.

The NSW Ministry of Health is currently funding the PRELUDE: Implementation of HIV pre-exposure prophylaxis with antiretroviral medications among people at high risk for HIV infection demonstration project in NSW. The expansion of access to PrEP for high risk gay men in both the public and private sector is a priority for the Ministry in 2015. Local sexual health clinics are also available to provide further information and support on the availability of PrEP in NSW.

Further References and Resources

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