HIV in Canada: A primer for service providers

Post-exposure prophylaxis (PEP)

Key Points

  • Post-exposure prophylaxis (PEP) is the prescription of HIV drugs after an actual or suspected exposure to HIV to prevent HIV transmission.
  • PEP must be administered as soon as possible, within 72 hours, after a suspected exposure to HIV.
  • PEP is a regimen of combination HIV drugs that needs to be taken every day for four weeks.
  • There is limited evidence regarding the level of protection that PEP provides.
  • PEP is the standard of care for exposures of healthcare workers (occupational exposures) but not sexual exposure and other types of exposure such as through injection drug use (non-occupational exposures).
  • There is varying availability of PEP across Canada for non-occupational HIV exposure.

Post-exposure prophylaxis (PEP) is the use of HIV drugs after an actual or suspected exposure to HIV to try to prevent HIV transmission. It should be started as soon as possible after exposure and involves taking medications every day for 4 weeks.

There is limited evidence that suggests providing PEP after a potential exposure to HIV can help reduce, but not eliminate, a person’s risk of HIV infection. Firstly, in monkey studies, taking PEP for one month protected almost all of the monkeys against infection by HIV-like viruses. Secondly, two studies that compared the number of HIV infections in people who took PEP with the number of infections in those who did not provided some evidence that taking PEP may reduce the likelihood of HIV transmission after a recent exposure by between 80% and 90%. However, these two studies were observational (not randomized, placebo-controlled trials) and the findings are therefore not definitive.

There is no direct evidence to support the use of combination HIV therapy instead of monotherapy, but because of the success of combination therapies in treating HIV infection, combination therapies are generally used for PEP. In experiments on monkeys, PEP was most effective when taken within 24 hours of exposure, but infections were sometimes prevented when PEP was taken as long as 72 hours after exposure. On the basis of this evidence, guidelines suggest that PEP should be started as soon as possible but can be prescribed up to 72 hours after the exposure.

Factors that can limit the effectiveness of PEP include poor adherence to daily pill taking, longer time to PEP initiation and continued exposures to HIV while taking PEP (PEP is only meant to reduce the risk from a single exposure).

The potential risks of PEP include drug toxicity and side effects, interactions with other medications and the development of drug-resistant strains of HIV (if infection occurs). A person who wants to use PEP will have their HIV risk assessed as this therapy is only meant to be used after a potential high-risk exposure. Also, an HIV test will need to be performed to confirm that the person starting PEP is HIV negative.

To improve the impact of PEP, additional prevention interventions should be used to help a person reduce their risk of infection during and after PEP use. There is some evidence to indicate that providing more comprehensive risk-reduction counselling to high-risk individuals accessing PEP can lead to a reduction in HIV transmission after PEP.

PEP is the standard of care for healthcare workers who have experienced a potential exposure to HIV. Accessibility of PEP for non-occupational exposures (consensual sex, sexual assault, sharing needles) varies across Canada. It is available at some hospital emergency departments and health clinics. Even in locations where PEP is available, there are very few health promotion campaigns and therefore awareness is low among both potential PEP users and doctors. The high cost of PEP, potentially more than $1,000 for a full course of medications, could also limit access to PEP. However, the drugs used for PEP may be covered by some private and public health insurance plans in Canada. Currently, only people who are aware of PEP, can either pay for or get coverage for the cost of PEP, and know where to access it can benefit from PEP.

Resources

Post-Exposure Prophylaxis for Prevention (PEP)

Post-exposure Prophylaxis (PEP) – CATIE fact sheet

Can we prevent infection with HIV after an exposure? The world of post-exposure prophylaxis (PEP)Prevention in Focus

The PEP Program at Clinique l’Actuel Programming Connection

Sources

  1. Cardo DM, Culver DH, Ciesielski CA, et al. A case-control study of HIV seroconversion in health care workers after percutaneous exposure. Centers for Disease Control and Prevention Needlestick Surveillance Group. New England Journal of Medicine. 1997 Nov 20;337(21):1485–90.
  2. Schechter M, do Lago RF, Mendelsohn AB, et al. Behavioral impact, acceptability, and HIV incidence among homosexual men with access to postexposure chemoprophylaxis for HIV. Journal of Acquired Immune Deficiency Syndromes. 2004 Apr 15;35(5):519–25.
  3. Barber TJ, Benn PD. Postexposure prophylaxis for HIV following sexual exposure. Current Opinion in HIV and AIDS. 2010 Jul;5(4):322–6.
  4. Poynten IM, Jin F, Mao L, et al. Nonoccupational postexposure prophylaxis, subsequent risk behaviour and HIV incidence in a cohort of Australian homosexual men. AIDS London England. 2009 Jun 1;23(9):1119–26.
  5. Heuker J, Sonder GJB, Stolte I, et al. High HIV incidence among MSM prescribed postexposure prophylaxis, 2000-2009: indications for ongoing sexual risk behaviour. AIDS London England. 2012 Feb 20;26(4):505–12.
  6. Roland ME, Neilands TB, Krone MR, et al. A randomized noninferiority trial of standard versus enhanced risk reduction and adherence counseling for individuals receiving post-exposure prophylaxis following sexual exposures to HIV. Clinical Infectious Diseases. 2011 Jul;53(1):76–83.
  7. Dodds C, Hammond G, Keogh P, et al. PEP talk: awareness of, and access to post-exposure prophylaxis among gay & bisexual men in the UK [Internet]. London: Sigma Research; 2006 Nov. Available from: www.sigmaresearch.org.uk/downloads/report06d.pdf [accessed March 10, 2014]