What Is PrEP and How Does PrEP Prevent HIV?

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It is estimated that 1.5 million people worldwide became newly infected with HIV in 2021. While this is a 32% decline in new infections since 2010, the risk of contracting the virus is still quite high. If you are HIV-negative but engage in risky sexual practices, you may have a higher chance of getting HIV. In that case, you can protect yourself and prevent HIV infection by using Pre-Exposure Prophylaxis (also called PrEP). Looking to learn more about HIV prevention? This article provides everything you need to know about PrEP for HIV and how it prevents HIV infection.

What Is HIV?

HIV — also known as human immunodeficiency virus — weakens your body’s immune system, reducing your ability to fight off infections. It targets a specific type of white blood cell in your immune system called the CD4+ T-cells. CD4+ cells play a vital role in detecting harmful pathogens such as viruses and bacteria so your body can start fighting them off.

When you get infected with HIV, the virus attaches to the surface of a CD4+ cell, gets inside it, and makes copies of itself. Then, it kills the infected CD4+ cell and releases more HIV copies into your bloodstream to attack other CD4+ cells. If left untreated, HIV can continue to damage your immune system and kill off CD4+ cells over time until you develop AIDS (or acquired immunodeficiency syndrome). 

Living with AIDS increases your chances of contracting opportunistic infections such as candidiasis, tuberculosis, pneumonia, and more. These are opportunistic infections because they often occur in people with weakened immune systems.

HIV Transmission

HIV is often present in the blood, vaginal fluid, pre-ejaculatory fluid, semen, breast milk, and rectal fluid. 

It can be transmitted by:

  • Sexual contact — oral, vaginal, and anal sex, and sharing of sex toys
  • Sharing of needles
  • Receiving a blood transfusion from an infected individual
  • Childbirth
  • Breastfeeding
  • Biting someone or being bitten by someone with the virus— when they break skin and draw blood
  • Undertaking body-modification procedures like piercings and tattoos with unsterilized tools

How To Prevent HIV?

There is currently no cure for HIV. Once you get the virus, it may remain in your body for life. Fortunately, you can protect yourself from the virus through the following ways:

  • Abstinence from sex
  • Engaging in safe sex practices that don’t involve the exchange of body fluids
  • Using condoms correctly every time you have sex
  • Avoiding sharing needles or using sterilized needles
  • Talking to your doctor about taking HIV prevention medicines like PrEP

What Is PrEP HIV?

PrEP is an HIV prevention drug used by people who have not yet been exposed to the virus. When taken as prescribed, it reduces your chances of getting the virus from sex by up to 99% and from injection drug use by up to 74%. PrEP for HIV can be administered as pills or shots.

FDA-approved PrEP medications include:


Truvada for PrEP is a once-daily prescription drug that contains two active ingredients — emtricitabine and tenofovir. It’s taken once a day every day for as long as you are at risk of getting HIV. It’s recommended for adolescents and adults who weigh at least 77 pounds (35 kg). Both males and females can use the drug.


Descovy is an HIV PrEP tablet taken once daily for as long as you are at risk. It contains two main ingredients — emtricitabine and tenofovir. The drug should be used by male adults and male adolescents who weigh at least 77 pounds (35 kg).

However, Descovy isn’t approved for use in individuals born female who are at risk for contracting HIV through receptive vaginal sex. This is because we do not yet know if the Descovy will work well in females.


Apretude is the only FDA-approved PrEP shot as of 2022. It contains cabotegravir as an active ingredient. This HIV PrEP drug is given as an intramuscular injection by a healthcare provider. It involves six shots per year.

People at risk of getting the virus through sex and weighing at least 77 pounds (35 kg) can use Apretude. However, it isn’t recommended for individuals who inject drugs as it may not be as effective.

Does PrEP Prevent HIV? How Does It Work? 

PrEP drugs like Truvada and Descovy belong to a class of antiviral drugs called nucleoside reverse transcriptase inhibitors (NRTIs). This means they stop HIV from making copies. They do this by blocking the protein called reverse transcriptase—this protein is needed for HIV to make copies.

When you take these drugs, they set up walls around your CD4+ cells, stopping HIV from crossing into your healthy cells and making copies of itself.

Unlike these pills, the Apretude shot is an integrase inhibitor. It stops the HIV virus from entering your healthy cells and reproducing more copies of itself.

Before starting the PrEP medication, talk to your doctor to take a test to confirm you are HIV-negative. HIV drug resistance may develop if you are HIV positive and take PrEP. This means the HIV virus in your body will continue to make copies of itself despite using antiretroviral medication. This is a problem because the virus learns how to avoid the ways that the drugs work against it, so the drugs become ineffective.

Note that while it protects you against HIV, PrEP won’t protect you from contracting other sexually transmitted infections ( STIs).

How Long Does PrEP Take to Work?

The simple answer is that it depends on your HIV risk factors. PrEP tablets reach maximum protection from HIV at about 7 days of daily use for receptive anal sex. For receptive vaginal sex and injection drug use, it takes about 21 days of daily use. If you don’t take the medication as prescribed, it increases your chances of contracting HIV.

As for the HIV PrEP shot, it will be administered by your healthcare provider once each month for the first 2 months. After that, you will get a shot of cabotegravir once every 2 months. The shot is long-acting and can stay in your body for 12 months or more after your last injection. 

Who Should Use PrEP?

PrEP should be used by people who do not have HIV/AIDS but are at risk of getting HIV. You may be a good candidate for PrEP if you:

  • Have had vaginal, anal, or oral sex in the past 6 months AND have a sexual partner living with HIV— detectable or unknown viral load
  • Have had vaginal, anal, or oral sex in the past 6 months AND have not used a condom consistently during sex
  • Have had vaginal, anal, or oral sex in the past 6 months AND have contracted a sexually transmitted disease (STD) in the past 6 months
  • Use injection drugs AND have an injection partner who has HIV
  • Use injection drugs AND share syringes, needles, or other equipment used to inject drugs
  • Have used Post-Exposure Prophylaxis (PEP) (which is a preventative drug started after the exposure of the virus. PrEP, on the other hand, is started before exposure) AND report continued high-risk behavior
  • Have used PEP multiple times

If you are a female with a partner who has HIV and considering conceiving a baby, talk to your doctor about PrEP HIV medication. It may be an option to help protect you from contracting the virus while you try to get pregnant.

Is PrEP Safe?

PrEP for HIV is safe. Some people taking the medication may experience side effects like headache, fatigue, nausea, stomach pain, and diarrhea. These side effects usually go away over time. If the side effects are severe or persist, talk to your doctor as soon as possible. 

Where Can You Get PrEP? 

Are you at risk of contracting HIV? PrEP may be right for you. Visit your doctor to get tested and know whether you are a good candidate for this HIV prevention drug. They will offer a prescription and work with you on a plan to help you prevent HIV. 

And if you have tested positive, you can still live a happy and fulfilling life. You should speak with your doctor about getting started on the right HIV medications. If you already have HIV/AIDS, you would not be a candidate for PrEP. 

  • “The Global HIV/AIDs Epidemic” via HIV.gov
  • “How effective is PrEP?” via CDC
  • “FDA Approves First Injectable Treatment for HIV Pre-Exposure Prevention” via FDA
  • “Nucleoside Reverse Transcriptase Inhibitor (NRTI)” via Clinical Info
  • “HIV Drug Resistance” via WHO
  • “HIV-1 Associated Opportunistic Infections” via StatPearls
  • “HIV Prophylaxis” via StatPearls
  • “HIV Prevention: Pre-Exposure Prophylaxis” via NIH