What to Do If You Are Accidentally Exposed to HIV

If you believe you may have been accidentally exposed to HIV, either through sex or other high-risk activities, there are medications, called post-exposure prophylaxis (or PEP), that can greatly reduce the risk of an infection.

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Examples of high-risk exposure include:

Post-exposure prophylaxis consists of a 28-day course of antiretroviral drugs, which must be taken completely and without interruption. In order to minimize the risk of infection, PEP must be started as soon as possible—ideally within one to 36 hours of exposure.

Some guidelines suggest that PEP can be administered within up to 72 hours of exposure, but it's important to understand that the chances of preventing infection are best the sooner you start treatment—before the virus has the opportunity to migrate from the site of entry and into the bloodstream and lymph nodes.

So the bottom line is to seek immediate attention. Do not wait. The moment an exposure occurs, go to your nearest emergency room or walk-in clinic. Do not wait until the morning to call your doctor.

PEP is also prescribed to health care workers who have had occupational exposure to HIV, such as through contact with infected blood or a needle-stick injury in a hospital or clinic setting.

How PEP Is Administered

Once you arrive at the hospital or clinic, you will be given a rapid HIV test to determine whether you are HIV positive or HIV negative.

  • If you are HIV positive, that means you have been previously exposed to HIV and are infected with the virus. A second test will be given to confirm the results, after which you will be sent to a health care worker for counseling and to discuss your results.
  • If you are HIV negative, you will be given an immediate course of two to three antiretroviral drugs that you will need to start immediately and take for four weeks. For less serious exposure, two drugs are usually prescribed. For more serious cases, such as rape or an occupational injury with a person of unknown or known HIV status, a third drug may be prescribed. (Some guidelines, however, routinely prescribe three drugs in all cases due to the higher tolerability and ease of use of newer-generation drugs).

You would then be advised about proper dosing, possible side effects, and adherence to therapy. Additional screening tests may be performed, if indicated (e.g., STIs, hepatitis B). Emergency contraception may also be prescribed in cases of rape or sexual assault.

If a rapid HIV test is not available, you will be given a standard HIV ELISA test and provided the necessary drugs to start treatment. You would then be advised of your results once lab tests are completed and told whether you need to continue treatment.

A follow-up HIV test would then need to be scheduled, usually within 4-6 weeks after completion of PEP.

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PEP in occupational settings has been shown to reduce the risk of HIV infection by 81 percent, according to a study published in the New England Journal of Medicine. No empirical data is available to quantify the effectiveness of PEP in cases of sexual assault or injecting drug exposure for two simple reasons:

  1. It is difficult to segregate exposures by type or severity in an emergency care setting.
  2. A clinical trial would require a "control group" of individuals who are exposed to HIV but are not given PEP in order to establish comparative effectiveness—an ethical impossibility.

That said, the cumulative results to date suggest that PEP can be effective in minimizing the risk of HIV transmission in cases of accidental, non-occupational exposure.

Additional Information

  • The cost of PEP may be covered by insurance (or your employer in cases of occupational exposure), but do not wait for confirmation before proceeding, particularly if it has been 24 hours or more since the exposure occurred.
  • PEP is not a morning-after pill. Once started, you need to complete the entire course of medication. Missing doses or stopping treatment prematurely can lead to the development of HIV drug resistance. If you are experiencing intolerable side effects, call your doctor or clinic immediately. Other drugs can usually be substituted.
  • If you are unsure if you've been exposed to HIV, go to your nearest hospital or clinic, or call an HIV hotline. A directory of AIDS hotlines can be found in the yellow pages under "AIDS, HIV Educational Referral, and Support Services" or "Social Service Organizations." They will be better able to advise you on your risk of exposure.
  • Persons at high risk for HIV should consider ways to prevent HIV before it begins. Today, there is a strategy called HIV pre-exposure prophylaxis (PrEP) in which the daily use of the drug Truvada can reduce the risk of getting HIV by around 95%.
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