Can PrEP Prevent HIV Infection?

Updated July 9, 2025

HIV pre-exposure prophylaxis (PrEP) is transforming the fight against HIV, offering a powerful tool for preventing new infections before they start. By taking preventive medication, individuals at risk for HIV transmission can dramatically reduce their chances of contracting HIV, empowering them to take control of their health and future. As awareness and access to PrEP expand, understanding how it works, who can benefit, and how to get started is essential for anyone interested in proactive sexual health and HIV prevention.

Pre-exposure prophylaxis is a method of HIV prevention that involves the use of antiretroviral (ARV) drugs. “Prophylaxis” isn’t a new idea — the term refers to treatments that prevent infection. Travelers are familiar with this practice if they’ve taken malaria drugs before departing for high-risk countries.

HIV-negative individuals using PrEP take ARV drugs prior to potential HIV exposure in order to reduce their risk of infection.

There are two medications available as a daily pill:

• Truvada (emtricitabine/tenofovir disoproxil fumarate): approved for all people at risk for HIV through sex or injection drug use.
• Descovy (emtricitabine/tenofovir alafenamide): approved for sexually active men and transgender women at risk for HIV through sex. Not approved for people at risk through receptive vaginal intercourse.

There are two medications that are available as injections available for people who are at risk of HIV transmission through sex:

• Apretude (cabotegravir extended-release injectable suspension): approved for adults and adolescents weighing at least 77 pounds. Administered every two months.
• Yeztugo (lenacapavir): The most recently FDA-approved PrEP drug, approved in June 2025. Administered as an injection every 6 months.

HIV PrEP medications work by preventing the reproduction of HIV, so if a person is exposed, the virus can’t establish infection in the body.

PrEP is not a cure for HIV, and it doesn’t protect against other sexually transmitted infections (STIs) or pregnancy. It’s important to continue using condoms consistently while you are on PrEP.

Taken consistently as prescribed, PrEP is about 99% effective for reducing HIV transmission through sex. The length of time it takes for maximum effectiveness varies by route of transmission:

• for receptive anal sex, PrEP pills reach maximum effectiveness after seven days of daily use
• for receptive vaginal sex and injection drug use, PrEP pills reach maximum effectiveness after 21 days of daily use.

Oral PrEP medications are estimated to be at least 74% effective for reducing HIV transmission through IV drug use. The injectable medications are not recommended for HIV prevention for individuals who inject drugs.

It is not known how long it takes for the injectable medications to reach maximum effectiveness.

Nausea, vomiting, fatigue, and dizziness are all potential side effects of PrEP pills within the first few weeks, but the symptoms are usually minor and resolve over time. Although uncommon, kidney damage is a more serious potential side effect, so people who take PrEP pills should have their kidney function monitored periodically.

The injectable medications can cause local reactions at the injection site, including pain, redness, itching, and swelling. Less common side effects of the injectables include nausea, dizziness, diarrhea, headache, and fatigue.

Yes, PrEP users must follow up with a health care provider every two or three months to confirm a negative HIV status. If a person becomes infected with HIV while taking PrEP medication, the virus can become resistant to that drug, so it's important to ensure that a new infection has not developed.

Regular STI testing is also recommended for people who are at risk for HIV transmission through sex. Additionally, people taking the oral forms of PrEP should have their kidney function monitored regularly.

Many insurance plans do cover PrEP, but it is important to check with your individual carrier.

Without insurance, PrEP can be expensive—out-of-pocket costs can be as high as $25,000 per year. However, there are many ways to obtain PrEP medications at low or no cost, including cost assistance programs directly through the manufacturers, clinical trials, and in some states, Medicaid. Individuals may also take advantage of local public health programs; contact your local health department for more information.

Schedule an appointment with your health care provider. They will be able to provide more information about the different kinds of PrEP, help determine what's right for you, and do preliminary testing to confirm it is safe for you to start taking the medication.

• PrEP Facts
• Centers for Disease Control (CDC)
• HIV.gov