PrEP & TasP

Millions of people around the world are helping to end the HIV epidemic using:

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

All three methods rely on people taking approved antiretroviral drugs. HIV-negative people use PrEP and PEP to stay HIV-negative, and people living with HIV use TasP to stay healthy and prevent transmission to others.

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. So far, the U.S. Food and Drug Administration has approved three options for PrEP:

  • A pill called Truvada® (approved in 2012)
  • A pill called Descovy® (approved in 2019)
  • An injection called Apretude® (approved in 2021).

Talk to your doctor to find out if PrEP may be right for you. We know that:

  • PrEP is very safe. 
  • PrEP is nearly 100% effective when used as prescribed.
  • PrEP is helping to end the HIV epidemic, but millions of people who could benefit from it are not accessing it.

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. For example, researchers are studying the possibility of an implant consisting of tiny rods that could 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.

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. 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."

PrEP and TasP FAQ

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

What is oral PrEP?


Oral PrEP refers to pills taken to prevent HIV. Truvada® is a pill consisting of an anti-retroviral (ARV) drug combination of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC). The FDA approved daily oral Truvada® for HIV pre-exposure prophlaxis (PrEP) in July 2012. Truvada® is available for doctors to prescribe as PrEP to anyone who is HIV-negative and wants to prevent HIV. It is also available in generic form (as opposed to name-brand).

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 trying to prevent HIV through receptive vaginal sex (e.g. cisgender women, transgender men, and nonbinary people assigned female at birth). PrEP must be prescribed by a doctor, so talk to your doctor to find out which option might be best for you.

What research has been done on oral 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 likelihood of contracting HIV 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 bodies were better protected than those who did not take the pills daily. In 2011, two additional studies also found Truvada® effective in reducing the likelihood of contracting HIV among heterosexual men and women.

Since these early PrEP studies, we have learned that PrEP is nearly 100% effective when taken as prescribed, and anyone can use it to help prevent HIV, including people of all genders and people who inject drugs. Studies have shown that PrEP is not as effective if it is not taken as prescribed.

What is injectable PrEP?


Injectable PrEP refers to a drug that is administered by a medical provider as an injection for the purpose of preventing HIV. In December 2021, the U.S. Food and Drug Administration approved the first PrEP injection, which is under the brand name Apretude®. People taking injectable PrEP receive one shot every 2 months. This is a great option for people who prefer to take bimonthly shots instead of daily pills to prevent HIV.

The option to take injectable PrEP was made possible by two major research studies conducted by the HIV Prevention Trials Network, HPTN 083 and HPTN 084. Together, these two studies showed that the drug cabotegravir is very safe and works extremely well to prevent HIV when it is injected into the buttock every 2 months. With a prescription from a doctor, anyone who is HIV-negative and wants to prevent HIV can take injectable PrEP.

How effective is PrEP at preventing HIV?


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. Truvada®, Descovy®, and Apretude® are all extremely effective.

What are side effects of PrEP?


PrEP may have side effects, and you should consult a medical provider if you have any concerns. While most people tolerate PrEP very well, possible side effects 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?
  • Do you have anal or vaginal 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 a 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.

Where can I get PrEP?


The best place to start is asking a doctor; PrEP can only be prescribed by a medical provider. Insurance companies cover the cost of PrEP, and there are also programs to help people pay for PrEP.  Find a location near you at PrEP Locator.

How do we know that "Undetectable" means "Untransmittable"?


"Undetectable" means that a person living with HIV has taken medicine to lower the amount of HIV in their body to the point where regular lab tests can not detect the virus. A series of large studies, starting with the HPTN 052 study in 2011, have scientifically demonstrated that Undetectable equals Untransmittable, meaning that HIV cannot be transmitted through sex from a person whose HIV is undetectable. This result was confirmed by other large studies, including studies called PARTNER 1, PARTNER 2, and Opposites Attract, whose combined results showed that HIV was never transmitted by a person whose HIV was undetectable, even after more than 126,000 individual sex acts without condoms. There is zero chance of HIV transmission through sex from a person whose HIV is undetectable.

An organization called Prevention Access Campaign (PAC) coined the term "Undetectable Equals Untransmittable," or "U=U." PAC works to spread the word about U=U. This is another example of researchers and advocates working together to end the HIV and AIDS epidemic. 

Keep Learning About HIV Prevention Methods