PrEP & TasP

There are currently three proven methods for preventing HIV transmission using anti-HIV drugs. These are:

  • Pre-Exposure Prophylaxis (PrEP)
  • Post-Exposure Prophylaxis (PEP)
  • Treatment as Prevention (TasP)

All three methods rely on approved antiretroviral drugs taken either by HIV-negative people to stay HIV-negative (PrEP and PEP) or by people living with HIV to prevent transmission to others (TasP).

Illustration of pill bottle and syringe depicting medication.
Illustration of pill bottle and syringe depicting medication. Illustration by Kimberly Carney / Fred Hutch

What is Pre-Exposure Prophylaxis (PrEP)?

Pre-Exposure Prophylaxis (PrEP) is an HIV prevention strategy that enables HIV-negative people to stay HIV-negative by taking anti-HIV drugs (also called antiretrovirals, or "ARVs") before they are exposed to HIV.

In 2012, the FDA approved a pill called Truvada for daily use as PrEP. Another PrEP pill called Descovy was approved in 2019. Talk to your doctor to find out if PrEP may be right for you. 

  • PrEP is very effective when used as prescribed.
  • PrEP works best in combination with regular HIV testing and other proven prevention methods, such as condoms or Treatment as Prevention (TasP).
  • PrEP is much less effective when used inconsistently.
  • It is important to schedule regular medical appointments for HIV testing and to monitor overall health while you are taking oral PrEP.

New methods to deliver PrEP over longer periods are also being studied. These methods could release anti-HIV drugs into the body over a period of several months to prevent HIV. Two methods under study include:

  • Injectables: shots that would be given by a medical provider. One major study so far has shown that this method of HIV prevention works for cisgender men and transgender women who have sex with men. Another major study showed that this method of HIV prevention is also highly safe and efficacious for cisgender women. Injectable PrEP is not yet available outside clinical trials.
  • Implantables: tiny rods that would be placed just beneath the surface of the skin by a medical provider. This method is still early in development.

Post-Exposure Prophylaxis (PEP)

Post-Exposure Prophylaxis (PEP), on the other hand, is a prevention technique that uses a short-term regimen of ARV pills after exposure to HIV.

PrEP and PEP Planned Parenthood Videos

What Is The PrEP Pill? 

What Is Post Exposure Prophylaxis (PEP)?

Undetectable means untransmittable. If there’s no virus circulating in your blood, then you can’t pass it on through sex…

What is Treatment as Prevention (TasP)?

Treatment as Prevention (TasP) refers to the use of anti-HIV drugs by someone who has HIV to stay healthy and to reduce the chance of transmitting HIV to others through sex, needle sharing, or during pregnancy and birth.

TasP works by decreasing the amount of HIV in the body. This makes a person’s blood, vaginal fluid, breast milk, and semen less likely to pass HIV to others. When people living with HIV reduce the amount of virus in the body to "undetectable" levels (known as "viral suppression"), the chance of transmitting HIV to others through sex is reduced to zero--even sex without condoms or PrEP.

TasP usually consists of three anti-HIV drugs taken daily as part of the drug regimen that keeps people living with HIV healthy.

The consistent and correct use of anti-HIV drugs to maintain decreased HIV in the body includes:

  • Taking anti-HIV drugs as prescribed by a medical provider
  • Regular medical appointments to monitor the amount of HIV in the body

People who start treatment soon after becoming HIV-positive will have improved health outcomes and live longer than those who start treatment later.


For more information on TasP watch:

What is the HIV Prevention Trials Network (HPTN)?

The HIV Prevention Trials Network (HPTN) is a worldwide collaborative clinical trials network that brings together investigators, ethicists, community, and other partners to develop and test the safety and efficacy of HIV preventions. The network focuses particularly on regions and communities that bear the highest burden of HIV infection. Founded in 2000 and funded by the National Institutes of Health, HPTN researches integrated strategies for HIV prevention, including antiretroviral drugs and behavioral interventions.

In Our Words


"PrEP, microbicides, and all these different acronyms and multisyllabic words that we have can be a little daunting, but you lower those barriers to the language, and then they realize that they know more about it than they even thought."


"One of the main lessons we’ve learned in the last thirty years is there’s not going to be a single solution to the HIV epidemic."

Truvada FAQ

Would you like to understand more about Truvada and how it works to prevent HIV? We have compiled a list of the questions most frequently asked by our community members, below.

What is Truvada®? What is Descovy®?


Truvada® is an anti-retroviral (ARV) drug combination of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC). It comes in the form of a pill. The FDA approved daily oral Truvada® for pre-exposure prophlaxis (PrEP) in July 2012. Truvada® is currently available for doctors to prescribe for use as PrEP for anyone who may be vulnerable to contracting HIV.

Descovy® is also an anti-retroviral (ARV) drug combination in the form of a pill that is slightly different from Truvada®. It was FDA-approved as PrEP in October 2019 and can also be prescribed by a doctor. The main difference between Truvada® and Descovy® is who can take it. Truvada® is approved for anyone to use as PrEP. Currently, Descovy® is not approved for use by people who are vulnerable to contracting HIV through receptive vaginal sex. We therefore focus more on providing information about Truvada® since it can be prescribed to anyone, while Descovy® cannot. More options for PrEP will continue to become available as the research continues.

Has there been research on PrEP?


Several studies have been conducted in countries around the world involving tens of thousands of diverse participants. In 2010, the iPrEx study published results that showed the daily use of oral Truvada® reduced the risk of HIV infection by 44% in HIV-negative men who have sex with men (MSM) and transgender women. The study found participants who had more Truvada® in their body were better protected than those who did not take the pills daily. In 2011, two additional studies also found Truvada® effective in reducing HIV infection among heterosexual men and women.

Two different studies have shown that PrEP is not effective if it is not taken as prescribed. The VOICE study, which evaluated oral and topical PrEP, and Fem-PrEP, which evaluated oral use of Truvada® as PrEP, were both conducted with heterosexual women in Africa. Neither study showed that PrEP worked with those study participants because a majority of the participants did not take the drug as instructed.

How effective is Truvada® as PrEP?


The level of HIV protection varies depending on how consistently PrEP is used. Those who take it as prescribed have significantly greater levels of protection (nearly 100%) than those who do not. Other than low adherence, no factors have been identified that appear to influence the effectiveness of PrEP in reducing sexual transmission of HIV. Descovy® and Truvada® are equally effective.

How should Truvada® be taken?


The FDA-recommended dose of Truvada® for PrEP is:

  • one tablet taken by mouth daily,
  • at about the same time every day,
  • with or without food.

If you miss a dose of Truvada® your doctor may advise you to take the missed pill as soon as you remember on that same day, but to not take more than one dose of Truvada® in a 24 hour period. While taking PrEP, you should visit the doctor at least every three months to test for HIV, side effects, and to discuss any problems that you may be having with drug adherence. 

What are side effects of Truvada®?


Truvada® may have side effects, and you should consult a medical provider if you have any concerns. Allergic reactions include fever, rash, upset stomach, vomiting, loose or watery stools, and achiness. Other possible side effects include runny nose, gas, itching, headache, dizziness, depression, increased cough, muscle pain or weakness, sleeping problems, darkening of the palms and/or soles, bone pain or loss of bone mineral density.

Who should take PrEP?


If you’re HIV-negative and looking to expand your HIV prevention regimen, PrEP might be right for you. Some questions to consider:

  • Is your main sexual partner someone living with HIV? In other words, are you part of a mixed-status couple?
  • Has a cisgender man recently penetrated or “topped” you during anal sex without a condom?
  • Have you been treated recently for an STI such as gonorrhea?
  • Have you used Post-Exposure Prophylaxis (PEP) more than once in the past year?
  • Do you use alcohol and/or drugs heavily; or, does your sex partner(s)?
  • Do you exchange sex for money, housing or other needs; or, does your sex partner(s)?
  • Has your partner recently threatened you with violence or physically harmed you?

If you answer “yes” to any of these questions, you should consider discussing PrEP with your doctor.

Who should not take PrEP?


People who have symptoms of acute HIV infection (symptoms similar to the flu) or who have kidney disease or reduced kidney health should not use PrEP.

Where can I get PrEP?


PrEP can only be prescribed by a medical provider. Some insurance companies cover the cost of PrEP.  Find a location near you at PrEP Locator or call 1-855-330-5479 to find out if you are eligible.

How should Truvada® be stored?


Truvada® should be stored at room temperature in its original container. The container should be kept tightly closed and out of the reach of children. Do not give Truvada® prescribed to you to other people.

Where can I get additional information on Truvada®?


Additional information on Truvada® can be found on the following website:

Keep Learning About HIV Prevention Methods