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Your Time-Sensitive Chance to Reduce your HIV Infection Risk
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HIV is an incurable disease, but it can be prevented.

The word ‘HIV’ brings in its wake the fear of an incurable disease and lifelong social stigma in most people. HIV (Human Immunodeficiency Virus) is a virus that progressively destroys the immune cells of an infected person. Over time, the person with HIV will have a diminished immune system. The final complicated outcome known as AIDS (Acquired Immunodeficiency Syndrome) is a condition where the person with HIV is no longer able to fight against daily infections.

Currently, there remains no cure for HIV infection. Once a person is infected with HIV, they will remain with the infection for the rest of their life. HIV infection can be transmitted through unprotected sexual contact, body fluid, needle sharing, and/or blood transfusion with an infected person.

The silver lining here is that with the improvement of medical research and proper medical care, we can control HIV. Patients with HIV who are receiving prompt treatment can still live a long and quality life.

In this article, we discuss the availability of PEP medication to reduce the risk of acquisition of HIV when a person may potentially be exposed to HIV. The awareness of PEP can be life-changing and life-saving.

What is PEP?

PEP (Post-Exposure Prophylaxis) is an anti-retroviral medication option that can be offered to a person to reduce the risk of HIV infection after a potential exposure. PEP medication must be started within the first 72 hours (3 days) after exposure. This is time-sensitive, and the earlier you start on PEP, the better your chances of avoiding getting HIV infection. Hence, every hour is vital and may make a difference; don’t hesitate!

It is also imperative to take note that though PEP significantly lowers a person’s risk of acquiring HIV (when appropriately taken), PEP does not 100% guarantee the prevention of HIV infection after exposure. You should still practice safe sex at all times.

When should I consider PEP?

You can consider PEP medication as an option if you are concerned about a high-risk exposure to HIV within the last 72 hours.

High-risk exposures include unprotected penetrative sex (vaginal or anal) with:

  • Partner(s) who have HIV
  • Partner(s) who are men who have sex with men
  • Partner(s) who are bisexual men
  • Partner(s) who are sex workers
  • Partner(s) who have a history of needle/syringe drug use
  • Sexual assault

If you are unsure of your risk of exposure to HIV, please do not hesitate to reach out to your trusted healthcare provider for further evaluation of your risk and whether you are a suitable candidate for PEP.

What is my risk of exposure to HIV infection?

A person’s risk of contracting HIV can be higher in situations such as:

  • If you have an untreated STD after STD testing 
  • If you have the presence of sore(s), ulcer(s), or wound(s) over your genital or anal region
  • Your sexual partner’s HIV RNA load is high or has an untreated HIV status (particularly in the early and late stages of untreated HIV)
  • If you are sharing syringes or needles or injections with a person with HIV

The risk of acquiring HIV infection also depends on the type of sexual intercourse a person engages in.

The risk increases as follows (from lowest to highest):

  1. Insertive vaginal sex
  2. Receptive vaginal sex
  3. Insertive anal sex
  4. Receptive anal sex

The risk of HIV transmission in oral sex is low, with no actual accurate estimation of risk. However, there are HIV cases documented through oral sex. If there is a history of receptive oral intercourse with ejaculation, it is worth discussing with your physician if PEP is necessary.

Sources such as blood, body fluid secretion such as vaginal fluid, semen, and breast milk may transmit HIV. Sources such as saliva, tears, sweat, urine, and faeces are not able to transmit HIV. The risk of HIV with other activities such as sharing sex toys, biting, touching semen, and saliva is very low and negligible.

If you have any concerns about your HIV risk of exposure, please consult your doctor as soon as possible, as PEP can only be given within the first 72 hours after exposure.

HIV concern
It is a cause for concern if you (and/or your partner) have sores, ulcers or wounds over your genital or anal region.

What does PEP entail?

PEP consists of a combination of anti-retroviral medications.

Drugs that have been recommended in PEP include:

  • Tenofovir/emtricitabine (Truvada) and Raltegravir (Isentress)
  • Tenofovir/emtricitabine (Truvada) and Dolutegravir (Tivicay)
  • Single drug- Tenofovir/Emtricitabine and Bictegravir (Biktarvy)

It is important to inform your doctor about your medical and medication history. This ensures your doctor prescribes the suitable PEP medication for you.

HIV in your immune system.

How effective is PEP?

PEP is clinically proven to be effective in reducing the risk of HIV infection in a person who is exposed to HIV if it is started within 2 hours (ideally) and not later than 72 hours after exposure.

Upon exposure to HIV via the skin and mucous membrane, HIV will replicate in the macrophages (a white blood cell that maintains the immune system by eating or engulfing pathogens such as bacteria and viruses).

Following the next 2 to 3 days, the viruses will multiply and replicate in the surrounding lymph nodes. In 3 to 5 days, the virus will be disseminated into the bloodstream and other parts of the body. A person’s HIV infective status will then be established and irreversible.

By understanding the timeline and events that will eventually occur in HIV replication, we now know that the PEP regimen is time-sensitive to block viral replication and has the best potency and effectiveness if given at the earliest possible time.

What are the common side effects of taking PEP?

The common side effects include lethargy, stomach upset, nausea and diarrhoea, and headache. Thankfully, the discomfort tends to be mild, and most patients can tolerate the full course of the PEP medication.

In rare cases, PEP can affect a person’s liver function. Your doctor will usually recommend blood tests before and after the completion of PEP medication.

Speak to your doctor to understand more about PEP's side effects and medication profiles.

What should I expect when I see my doctor for a PEP consultation?

Your doctor will obtain a relevant history to assess your risk of exposure to HIV. Your medical history is also important to understand any medical condition or long-term medication that may interfere with the PEP medication. Your doctor will then offer you baseline blood tests before starting on PEP medication. You will also be counselled on the side effects to anticipate when you are on PEP.

What should I do after the completion of PEP?

Your doctor will usually schedule a follow-up appointment with you. You will be advised to get blood tests done upon completion of PEP to ensure you do not develop any long-term side effects from the medications. You will also be offered an HIV test to check your status at the end of your PEP course. It is good practice to consider a comprehensive STD screening in view of the recent exposure risk.

HIV test
Your HIV status can be checked with HIV blood tests.

Who is not suitable for PEP?

PEP is not suitable for anyone who has repeated exposure risk to HIV from unprotected sex. As the name suggests, PEP is used only for emergency circumstances. In frequent high-risk exposure to HIV situations, you may discuss with your doctor about PrEP (Pre-Exposure Prophylaxis) option instead.

PEP is also not suitable if you are known to be HIV positive or if you have a history of hepatitis. Due to how strong a PEP regimen can be and its potential side effects, you should consult your doctor before commencing.

PrEP is suitable for repeated high-risk exposures to HIV.

Can I take PEP every time I have frequent unprotected sex?

No, you should only consider PEP during emergencies. If you are concerned about the repeated high risk of exposure from your sexual encounters, you should speak to your doctor to consider PrEP HIV medication instead.

Key take-home message

While HIV is incurable, PEP medication can be life-saving as it can effectively reduce the risk of HIV infection when taken promptly within the first 72 hours of exposure. If you are uncertain of your encounter and are considering PEP, please contact your healthcare provider as soon as possible.


  1. DeHaan E, McGowan JP, Fine SM, et al. PEP to Prevent HIV Infection [Internet]. Baltimore (MD): Johns Hopkins University; 2022 Aug 11.
  2. “PEP,” 2023, https://www.cdc.gov/hiv/basics/pep.html.
  3. Beekmann SE, Henderson DK. Beekmann SE, et al. Prevention of human immunodeficiency virus and AIDS: postexposure prophylaxis (including health care workers). Infect Dis Clin North Am. 2014 Dec;28(4):601-13.
  4. Ford N, Shubber Z, Calmy A, Irvine C, Rapparini C, Ajose O, Beanland RL, Vitoria M, Doherty M, Mayer KH. Ford N, et al. Choice of antiretroviral drugs for postexposure prophylaxis for adults and adolescents: a systematic review. Clin Infect Dis. 2015 Jun 1;60 Suppl 3:S170-6. 
  5. John SA, Quinn KG, Pleuhs B, Walsh JL, Petroll AE. John SA, et al. HIV Post-Exposure Prophylaxis (PEP) Awareness and Non-Occupational PEP (nPEP) Prescribing History Among U.S. Healthcare Providers. AIDS Behav. 2020 Nov;24(11):3124-3131.
  6. “GUIDELINES,” 2019, https://www.eacsociety.org/media/guidelines-11.1_final_09-10.pdf.

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