PEP is for any HIV-negative person who has experienced a high-risk situation for HIV exposure within the last 72 hours.

If you think you are in this situation, the first thing to do is to consult a healthcare professional without any delay. A professional assessment is always necessary to determine if PEP is the right solution for you.

What types of risks can justify PEP?

The assessment will focus on exposures that present a significant risk of HIV transmission. The most common examples include:

• Sexual exposures: Anal or vaginal intercourse without a condom, a condom breaking, or sexual assault.
• Blood-related exposures: Sharing injection material or an accidental injury with a potentially contaminated object.

Risk assessment: an essential step

Before prescribing PEP, the healthcare professional must evaluate the actual level of risk. This confidential discussion takes into account factors like the type of exposure, the status of the source partner (if known, and if their viral load is undetectable, U=U), and your own HIV status, confirmed by a rapid test.

In which cases is PEP generally not indicated?

• If you are already on PrEP with good adherence.
• If the exposure occurred more than 72 hours ago.
• If the risk is judged to be very low or nil after assessment (e.g., oral sex).
• If you are already living with HIV (a full treatment regimen is needed then, not PEP).

The key message is: when in doubt, consult immediately. It is better to have a consultation for nothing than to leave a risk unmanaged.

This is an excellent question because even though the acronyms are similar, their roles are complete opposites.

The best way to see the difference is to compare the regular birth control pill to the morning-after pill.

PrEP: your planned, preventive protection

Think of PrEP as the "birth control pill" for HIV.

• Its role: It is a proactive protection that you take continuously before a potential exposure to HIV.
• How it's taken: On a regular basis (a daily pill or an injection every two months).
• Who it's for: For HIV-negative people who want continuous protection against HIV.

PEP (or PPE): your emergency solution after a risk

Think of PEP as the "morning-after pill" for HIV.

• Its role: It is an emergency treatment that is taken after a high-risk situation.
• How it's taken: It is a full 28-day course of treatment that must be started within a maximum of 72 hours after the risk.
• Who it's for: For HIV-negative people who have experienced a potential exposure and were not on PrEP.

In summary:

• PrEP = PRE-exposure. It is a continuous preventive strategy.
• PEP = POST-exposure. It is a one-time emergency treatment.

Yes, PEP is an effective strategy for preventing HIV after different types of high-risk exposure, whether sexual or blood-related.

However, the fact that PEP works does not mean it is necessary or recommended after every situation. A professional assessment is always crucial to determine if the risk of transmission justifies the treatment.

The main types of exposure where PEP is an effective option

• Sexual exposures: Highly effective after anal or vaginal intercourse without a condom, or in case of a condom accident (breaking, slipping).
• Sharing of injection equipment: A key intervention in cases of sharing syringes or needles.
• Occupational exposures: Used by healthcare personnel in case of a needlestick injury or blood contact.

Why is risk assessment so important?

Even for a risky exposure, a discussion with a healthcare professional is essential because:

• The level of risk varies: Receptive anal sex carries a much higher risk than other types of contact.
• The status of the source partner is key: If your partner is living with HIV but has an undetectable viral load (U=U, Undetectable = Untransmittable), the risk is zero and PEP is not necessary.
• Some contacts pose no risk: HIV is not transmitted through saliva or skin contact without an open wound. PEP is not indicated in these cases.

In short, PEP is a powerful tool, but its prescription always depends on a rigorous assessment of the actual risk. When in doubt, always consult.

How effective is PEP?

When used correctly, PEP (post-exposure prophylaxis) is a highly effective emergency intervention to prevent HIV infection. Its success depends on two rules: act fast and take the full treatment.

Rule #1: Act as quickly as possible

This is the most important factor. PEP must be started as soon as possible after the exposure, ideally within the first few hours, and no later than 72 hours after. Beyond that window, it is no longer recommended. The sooner treatment begins, the better its chances of stopping the virus before it takes hold.

Rule #2: Take the full treatment

PEP is not a single dose. It is a course of antiretroviral medication taken every day for 28 days. Stopping early or missing doses reduces protection.

What does recent evidence show?

The "over 80%" figure you may have come across comes from a 1990s study of health care workers using a single medication (AZT). It does not reflect current treatments.

Today's PEP combines several modern antiretrovirals that are more potent and better tolerated. Comparing PEP to a placebo would be unethical, so there is no exact percentage for these treatments. Recent evidence is nonetheless very reassuring. In studies published in recent years on the combinations preferred today, no HIV infections were observed.

The rare infections reported with PEP are mostly explained by a new exposure after the treatment ended, and sometimes by a late start or by stopping before the full 28 days. That is why the two rules above matter.

After PEP

HIV testing is needed at the start of treatment and in the months that follow to confirm that PEP worked. This follow-up is provided by a physician. Our team can help direct you to available resources.

If you find yourself needing PEP more than once, PrEP may offer better day-to-day protection. It is taken before exposure rather than after. Learn more about toutPrEP

Think you were exposed to HIV in the last 72 hours? Visit our PEP page

This information is provided for informational purposes only, is not exhaustive, and may change. It does not replace an individual assessment by a health care professional.