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HIV Prevention Basic Questions and Answers

December 11, 2013

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HIV Prevention Basic Questions and Answers

Today, more tools than ever are available to prevent HIV. In addition to limiting your number of sexual partners, never sharing needles, and using condoms correctly and consistently, you may be able to take advantage of newer biomedical options such as pre-exposure and post-exposure prophylaxis.

How Can I Prevent Getting HIV From Anal or Vaginal Sex?

Not having sex is the most effective way to prevent HIV. If you are sexually active, the following steps can reduce your risk of getting HIV:

  • Choose one partner and agree to be sexually active only with each other (mutual monogamy). It is still important that you and your partner get tested for HIV and share your test results with one another. Some people choose to keep using condoms in a mutually monogamous relationship for further protection from HIV and other sexually transmitted infections (STIs).
  • Limit the number of people you have sex with, if you have more than one partner. The fewer partners you have, the less likely you are to have sex with someone who is infected with HIV or another STI.
  • Use condoms correctly, every time you have sex.
  • Choose less risky sexual behaviors. Anal and vaginal sex are the highest-risk sexual activities for HIV transmission. Oral sex carries much less risk.
  • Get tested and treated for STIs and insist that your partner does too. STIs increase the risk of getting or spreading HIV. Find an STI testing site.
  • Talk to your doctor about HIV medicine to prevent HIV infection (known as pre-exposure prophylaxis, or PrEP) if you routinely have unprotected sex with someone who may be HIV-positive.
  • See a doctor right away (within 3 days) if you have a single experience of unprotected sex with someone who is or may be HIV-positive. Starting medicine immediately (known as post-exposure prophylaxis, or PEP) and taking it for a month reduces the chance of getting HIV.
  • Get tested for HIV. To find a testing site near you, call 1-800-CDC-INFO (232-4636), visit the National HIV and STD Testing Resources page, text your ZIP code to KNOW IT (566948), or use a home testing kit.


How Can I Prevent Getting HIV From Oral Sex?

Oral sex involves giving or receiving oral stimulation (i.e., sucking or licking) to the penis (fellatio), the vagina (cunnilingus), or the anus (anilingus). Most types of oral sex carry little to no risk of HIV. The highest oral sex risk is to individuals performing fellatio on an HIV-infected man, with ejaculation.

Factors that may increase the risk of HIV transmission through oral sex are oral ulcers, bleeding gums, genital sores, and the presence of other sexually transmitted infections.

Although anilingus (rimming) carries little to no risk of transmitting HIV, it does come with a high risk of transmitting hepatitis A and B, parasites, and other bacteria to the partner who is doing the rimming.

To reduce your risk of HIV or other infections during oral sex or oral-anal contact, you can use barriers such as condoms, natural rubber latex sheets, dental dams, or cut-open non-lubricated condoms. See Tips for Using Condoms and Dental Dams.

How Well Do Condoms Prevent HIV?

When used correctly and consistently -- every time you have sex -- condoms are highly effective in preventing HIV infection. Latex condoms provide the best protection against HIV. Polyurethane (plastic) or polyisoprene (synthetic rubber) condoms are good options for people with latex allergies. Natural membrane (such as lambskin) condoms are porous, meaning that infections can pass through them, and therefore do not protect against HIV and certain other sexually transmitted infections (STIs).

Because condoms cover only the penis, they are more effective at preventing STIs transmitted through body fluids, like gonorrhea, chlamydia, and HIV. Condoms provide less protection against STIs spread through skin-to-skin contact like human papillomavirus (genital warts), genital herpes, and syphilis.

We do not yet have research on how well female condoms prevent HIV and other STIs when used for anal sex. But we do know that HIV cannot pass through a female condom. Also, unlike latex male condoms, it is safe to use any kind of lubricant with female condoms (see "Can using a lubricant help reduce my HIV risk?").

For more information, see Tips for Using Condoms and Dental Dams.

Can Using a Lubricant Help Reduce My HIV Risk?

Yes. For anal sex, using water- or silicone-based lubricant with a latex condom helps to minimize damage to the rectum during sex, reduce condom breakage, and prevent the transmission of HIV and some other STIs. For vaginal sex, if dryness is a concern, using water- or silicone-based lubricant can prevent irritation and the condom breaking.

Oil-based lubricants and products containing oil such as hand lotion, Vaseline, or Crisco should not be used with latex condoms because they can weaken the condom and cause it to break. For condoms made of polyurethane or polyisoprene, it's safe to use lubricants that contain oil.

Lubricants containing nonoxynol-9 should not be used because they can irritate the lining of the vagina or anus and increase the risk of getting HIV.

Can Male Circumcision Prevent HIV?

Male circumcision reduces the risk that a man will get HIV from an infected female partner, and also lowers the risk of other sexually transmitted infections (STIs), penile cancer, and infant urinary tract infection. Studies have not consistently shown that it prevents HIV among men who have sex with men. Circumcision is only partly effective and should be used with other prevention measures. Men who are considering circumcision should weigh its risks and costs against its potential benefits. For more information on male circumcision and HIV, see CDC's male circumcision site.

Can I Take Medicines to Prevent Getting HIV?

Yes. You should consider pre-exposure prophylaxis (PrEP) if you routinely have sex without using a condom, especially if your sex partner is HIV-positive or has HIV risks (for example, they inject drugs or are having sex with other people) or if you have recently been diagnosed with a sexually transmitted infection. PrEP involves taking a pill (brand name Truvada) every day that contains two HIV medicines. These are the same medicines used to reduce the level of virus in people who are already infected.

You and your health care provider may consider the following factors in deciding whether PrEP is right for you:

  • Only people who are HIV-negative should use PrEP. HIV testing is required before starting PrEP and every 3 months while taking PrEP.
  • PrEP should never be seen as the first line of defense against HIV. Researchers have only studied it when used with other prevention efforts like regular HIV testing and condoms.
  • Because PrEP involves daily medicine and frequent visits to a health care provider, it may not be right for everyone.
  • PrEP can cause side effects like an upset stomach or loss of appetite but these are mild and usually go away within the first month.

Can I Take Medicines to Prevent HIV After Exposure?

Post-exposure prophylaxis, or PEP, is a 4-week course of drugs that may prevent HIV infection for people who think they may have been recently exposed. PEP is used to prevent HIV after possible exposure during a single event; it is not intended for long-term use. For example, health care workers can be exposed on the job through infected needles, sharp instruments, or body fluids. Others can be exposed through sexual assault or during episodes of unprotected sex or needle-sharing injection drug use.

PEP consists of two or three antiretroviral medicines prescribed on the basis of your likely exposure risk. These medicines keep HIV from making copies of itself and turning into infection. To be effective, PEP must begin as soon as possible, but always within 72 hours (3 days) of a possible exposure. Keep in mind that PEP should only be used in situations right after a potential exposure. It is not a substitute for other proven HIV prevention methods, such as correct and consistent condom use.

Because there still may be some risk of HIV infection, you should continue to use condoms with sex partners while taking PEP. This will help avoid spreading the virus to others if you do become infected.

For more information on preventing exposure to HIV, see the PEP Q&A, the CDC fact sheet, "Occupational HIV Transmission and Prevention Among Health Care Workers," or the PEPline page.

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This article was provided by U.S. Centers for Disease Control and Prevention. Visit the CDC's website to find out more about their activities, publications and services.
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