Preventing Sexual Transmission of HIV

How Can You Prevent Getting or Transmitting HIV through Sex?

There are powerful tools to prevent HIV transmission through anal or vaginal sex, including:

• PrEP. If you don’t have HIV (are HIV-negative), you can take HIV prevention medicine known as PrEP (pre-exposure prophylaxis) to prevent getting HIV. PrEP can be pills or shots. PrEP is highly effective when taken as prescribed.
• PEP. If you think you may have been exposed to HIV, PEP (post-exposure prophylaxis) is a short course of HIV medicine taken within 72 hours after a possible exposure to HIV to prevent the virus from taking hold in your body.
• HIV treatment as prevention. If you have HIV, take HIV treatment prescribed. People with HIV who take HIV medicine (known as antiretroviral therapy or ART) as prescribed and get and keep an undetectable viral load can live long and healthy lives and will not transmit HIV to their HIV-negative partners through sex. This is sometimes called HIV treatment as prevention or “undetectable = untransmittable” (U=U).

Read more about these and other ways to prevent getting or transmitting HIV through sex, below:

• Ways to Prevent Getting HIV (information for people who don’t have HIV)
• Ways to Prevent Passing HIV to Others (information for people with HIV)

*You can also get or transmit HIV through injection drug use by sharing needles, syringes, or other drug injection equipment. Learn more about how you can prevent getting or transmitting HIV from injection drug use. Pregnant people with HIV can also pass HIV to their babies. Learn more.

Ways to Preventing Getting HIV

If you don’t have HIV (are HIV-negative), you have several options to protect yourself from getting HIV through vaginal or anal sex. The more of these actions you take, the safer you can be.

To prevent getting HIV through sex, you can:

• Understand the risks of different sexual activities. HIV is mainly spread by having anal or vaginal sex without a correct use of a condom or without taking medicines to prevent or treat HIV. You can't get HIV from sexual activities that don't involve contact with semen, vaginal fluid, or blood. Here is some information about the chance of getting HIV from different sex activities.
  • Anal sex is the riskiest type of sex for getting or transmitting HIV. Either partner—the insertive partner (top) or the receptive partner (bottom)—can get HIV, but it is much riskier for an HIV-negative person to be the receptive partner. That’s because the lining of the rectum is thin and may allow HIV to enter the body during anal sex. Learn more.
  • Vaginal sex also carries a risk for getting HIV, though the chance is lower than receptive anal sex. Most women who get HIV get it from vaginal sex, but men can also get HIV from vaginal sex. Learn more.
  • Oral sex is when the mouth touches the penis, vagina, or anus. There is little to no risk of getting or transmitting HIV from oral sex. Learn more.
  • Sexual activities that don’t involve contact with body fluids (e.g., touching) carry no chance of HIV transmission.
• Take PrEP. If taken as prescribed, PrEP greatly reduces your chance of getting HIV from sex and injection drug use. It is much less effective when it is not taken as prescribed. PrEP may be right for you if you do not have HIV, you have had anal or vaginal sex in the past 6 months, and you:
  • Have a sexual partner with HIV (especially if the partner has an unknown or detectable viral load); or
  • Have not consistently used a condom; or
  • Have been diagnosed with an STI in the past 6 months.
  PrEP is also recommended for people who inject drugs and have an injection partner with HIV, or have shared needles, syringes, or other injection equipment, and those who have been prescribed PEP and report continued behavior may expose them to HIV or have used multiple courses of PEP. You may choose to take PrEP even if the behaviors listed above don’t apply to you. Find a PrEP provider in your area.
• Take PEP if you think you may have recently been exposed to HIV. If you’re HIV-negative or don’t know your HIV status and think you may have been recently exposed to HIV, talk about PEP right away with a health care provider, an emergency room doctor, an urgent care provider, or in some states a pharmacist. The sooner you start PEP, the better; PEP must be started within 72 hours (3 days) after a recent possible exposure to HIV. If you’re prescribed PEP, you’ll need to take it daily for 28 days. Keep in mind that you will not get HIV if your HIV-positive partner is taking HIV medicine as prescribed and their viral load is undetectable.
• If your partner has HIV, encourage them to get and stay on HIV treatment. Taken as prescribed, HIV medicine reduces the amount of HIV in the blood (the viral load) to a very low level. This is called viral suppression. HIV medicine can also make the viral load so low that a standard lab test can’t detect it. This is called having an undetectable viral load. People with HIV who take HIV medicine as prescribed and get and keep an undetectable viral load can live long and healthy lives and will not transmit HIV to their HIV-negative partners through sex. Most people taking antiretroviral therapy as prescribed can get an undetectable viral load within 6 months. Learn more about HIV treatment as prevention.
• Use condoms. Condoms are highly effective at preventing HIV and some other STIs like gonorrhea and chlamydia. Learn the right way to use condoms.
• Get tested and treated for other STIs and encourage your partners to do the same. If you are sexually active, get tested at least once a year. Having other STIs increases your chance of getting HIV. STIs can also have long-term health consequences. Find an STI testing site.
• Reduce your number of sexual partners. This can lower your chances of having a partner who could transmit HIV to you. The more partners you have, the more likely you are to have a partner with HIV whose viral load is not suppressed or to have a sex partner with an STI. Both these factors can increase the chance of HIV transmission.
• Decide not to have sex. Not having sex (also known as abstinence) is a 100% effective way to prevent HIV, other STIs, and pregnancy. You can be abstinent at different times in your life for different reasons that may change over time.
• Know your HIV status. The only way to know your HIV status is to get tested. Knowing your status can give you important information and help you make good decisions to prevent getting or transmitting HIV. Find an HIV testing site near you.

Ways to Prevent Passing HIV to Others

If you have HIV, there are many actions you can take to prevent transmitting HIV to an HIV-negative partner through sex.

• Get into care and take HIV medicine. This is the most important thing people with HIV can do to stay healthy. If taken as prescribed, HIV medicine reduces the amount of HIV in your blood (your viral load) to a very low level, which keeps your immune system working and prevents illness. This is called viral suppression. HIV medicine can also make your viral load so low that a standard lab test can’t detect it. This is called having an undetectable viral load. People with HIV who get and keep an undetectable viral load can live a long and healthy life and will not transmit HIV through sex. That’s why people say “U=U” or “Undetectable=Untransmittable.” Follow your healthcare provider’s advice and take your HIV medicine as prescribed. Most people taking antiretroviral therapy as prescribed can get an undetectable viral load within 6 months. Learn more about HIV treatment as prevention.
• Talk to your HIV-negative partners about PrEP, medicine they can take to prevent getting HIV. (Read about PrEP, above).
• Talk to your HIV-negative partners about PEP, if they may have been exposed to HIV within the past 72 hours. (Read about PEP, above).
• Use condoms. Condoms are highly effective in preventing HIV and other STIs, like gonorrhea and chlamydia. Learn the right way to use condoms.
• Understand the risks of different sexual activities. HIV is mainly spread by having anal or vaginal sex without a condom or without taking medicines to prevent or treat HIV. You can't get HIV from sexual activities that don't involve contact with semen, vaginal fluid, or blood. (Read more).
• Get tested and treated for other STIs and encourage your partners to do the same. If you are sexually active, get tested for STIs at least once a year. STIs can have long-term health consequences and can also increase your chances of transmitting HIV. Also, encourage your partners who are HIV-negative to get tested for HIV. Use HIV.gov’s HIV Services Locator to find HIV and STI testing sites nearby.

Learn More

Learn more by visiting CDC’s HIV Prevention Basics. You can also get information on how to protect yourself and your partner that is tailored to meet your needs from CDC’s HIV Risk Reduction Tool.