What Is PrEP and How Does It Prevent HIV?
If you've been following conversations about HIV prevention, you've likely come across the term PrEP. It's talked about in clinics, community health centers, and sexual health campaigns — and for good reason. PrEP is one of the most powerful tools available today for preventing HIV. But what exactly is it, how does it work, and is it right for you? This article breaks it all down in plain, straightforward language.
What Is PrEP?
PrEP stands for Pre-Exposure Prophylaxis. "Pre-exposure" means you take it before coming into contact with HIV, and "prophylaxis" is a medical term for a treatment that prevents a disease rather than curing it. In simple terms, PrEP is a medication taken by HIV-negative people to significantly reduce their risk of contracting HIV.
Currently, there are two main forms of PrEP approved by the U.S. Food and Drug Administration (FDA):
- Truvada (emtricitabine/tenofovir disoproxil fumarate) — the original daily oral PrEP pill, approved since 2012.
- Descovy (emtricitabine/tenofovir alafenamide) — a newer daily oral pill approved in 2019, available for certain populations.
- Apretude (cabotegravir) — a long-acting injectable form of PrEP, administered by a healthcare provider every two months. Approved by the FDA in 2021, this option is ideal for people who prefer not to take a daily pill.
How Does PrEP Work?
To understand how PrEP works, it helps to know a little about HIV itself. HIV (Human Immunodeficiency Virus) attacks the body's immune cells, specifically CD4 T-cells, and uses them to make copies of itself. Over time, without treatment, HIV can overwhelm the immune system and lead to AIDS (Acquired Immunodeficiency Syndrome).
PrEP medications work by blocking the enzymes HIV needs to replicate inside the body. When you take PrEP consistently, the active ingredients build up in your bloodstream and tissues — particularly in places where HIV exposure is most likely, such as rectal, vaginal, and genital tissues. If HIV enters your body, the medication essentially stops the virus from making copies of itself and establishing a permanent infection.
Think of it like a security system: PrEP doesn't stop HIV from entering the body, but it prevents the virus from "setting up shop" and spreading.
How Effective Is PrEP?
When taken as directed, PrEP is highly effective. According to the Centers for Disease Control and Prevention (CDC):
- Daily oral PrEP reduces the risk of HIV from sex by approximately 99% when taken consistently.
- For people who inject drugs, daily oral PrEP reduces the risk of HIV by at least 74%.
- The injectable form, Apretude, was shown in clinical trials to be 66% more effective than daily oral PrEP in one key study group.
It's important to note that the word "consistently" matters here. Missing doses lowers the level of protection. For the daily pill to be most effective, it also needs time to build up in the body — typically about 7 days for anal sex and approximately 21 days for vaginal sex or injection drug use.
Who Should Consider PrEP?
PrEP is not only for one specific group — it's for anyone who is HIV-negative and at substantial risk of HIV infection. The CDC recommends discussing PrEP with a healthcare provider if any of the following apply to you:
- You are sexually active and do not consistently use condoms, especially with partners whose HIV status you don't know.
- You have had a sexually transmitted infection (STI) in the past six months.
- You have an HIV-positive partner (especially if trying to conceive).
- You inject drugs, particularly if you share needles or equipment.
- You have multiple sexual partners.
PrEP is approved for use in adults and adolescents who weigh at least 35 kg (about 77 lbs). It can also be safely used during pregnancy and breastfeeding in many cases — talk to your healthcare provider for personalized guidance.
Does PrEP Protect Against Other STIs?
This is a common and important question. PrEP only protects against HIV — it does not prevent other sexually transmitted infections such as chlamydia, gonorrhea, syphilis, or herpes. This is why healthcare providers recommend combining PrEP with regular condom use for the most comprehensive protection. Regular STI testing is also a crucial part of staying on a PrEP regimen.
What Are the Side Effects?
PrEP is generally well-tolerated. Some people experience mild side effects when they first start, including:
- Nausea or upset stomach
- Headaches
- Fatigue
- Diarrhea
These side effects typically go away within the first few weeks. More rarely, Truvada can affect kidney function or bone density over time, which is why regular check-ups every three months are a required part of being on PrEP. Your provider will monitor your kidney function and overall health throughout your time on the medication.
How Do You Get PrEP?
PrEP requires a prescription from a licensed healthcare provider. The process generally involves:
- An HIV test to confirm you are HIV-negative before starting
- A kidney function test and STI screening
- A discussion with your provider about your risk factors and which form of PrEP is best for you
- A follow-up appointment every three months for ongoing HIV testing, STI screening, and health monitoring
PrEP is available through primary care doctors, sexual health clinics, Planned Parenthood locations, and community health centers. Cost should not be a barrier — most insurance plans, including Medicaid, are required to cover PrEP with no out-of-pocket cost under the Affordable Care Act. For those without insurance, programs like Gilead's Advancing Access and federal programs may cover costs entirely.
PrEP and the Bigger Picture of HIV Prevention
PrEP represents a major milestone in the global fight against HIV. The CDC estimates that approximately 1.2 million people in the United States could benefit from PrEP, yet as of recent data, only a fraction of eligible individuals are currently using it. Increasing access and awareness is a public health priority.
PrEP works best as part of a comprehensive prevention strategy that may also include consistent condom use, regular testing, open communication with partners, and — when applicable — treatment as prevention (meaning that an HIV-positive person on effective treatment with an undetectable viral load cannot transmit the virus, a concept known as U=U: Undetectable = Untransmittable).
Take the Next Step: Talk to a Provider and Get Tested
Whether you're curious about PrEP for yourself or for someone you care about, the most important step you can take is to get tested and talk to a healthcare provider. An HIV test is quick, confidential, and widely available — at clinics, pharmacies, community health centers, and even at home with FDA-approved at-home test kits.
Knowing your HIV status is the foundation of any prevention plan. If you test negative and your lifestyle puts you at elevated risk, PrEP could be a life-changing option for you. You deserve access to every tool available to protect your health — and PrEP is one of the most effective ones we have.
Ready to take control of your sexual health? Find a testing site or PrEP provider near you today. It's confidential, often free or low-cost, and it could make all the difference.