HIV prevention strategies encompass a range of approaches, both non-medical and medical. Non-medical methods include the use of barrier methods, abstinence, communication, and education; medical approaches may include the use of PrEP (Pre-Exposure Prophylaxis), PEP (Post-Exposure Prophylaxis) and TasP (Treatment as Prevention).

We believe in a comprehensive approach to HIV prevention that considers both medical and non-medical alternatives that are accessible to all. Ideally, a combination of strategies can be effective in reducing the likelihood of HIV transmission. Nonetheless, people should talk to their doctor or their sexual health practitioner to make an informed decision on what works best for them according to their lifestyle and personal preferences.

The choice of HIV prevention and management will differ at a pre-exposure stage (where a person has not yet been exposed to the virus) compared to post-exposure (a stage following exposure to the virus). Throughout this article we will explain how HIV is transmitted and what can be done to prevent or manage it at different stages in a person’s journey.

At ViiV Healthcare we strive for a health-informed public and community. The onus of preventing HIV shouldn’t fall exclusively on people living with the virus — we are all in it together, and we can all help reduce HIV transmission by making well-informed decisions.


Understanding how HIV is transmitted is key to preventing it. HIV can only be transmitted through certain bodily fluids from an individual who is living with HIV and has a detectable viral load. These fluids include semen, pre-seminal fluids, rectal fluids, vaginal fluids, blood, and breast milk.1 The most common method of HIV transmission is via anal or vaginal sex, and through intravenous drug use (i.e. sharing needles or syringes).2 HIV transmission is limited to direct contact with the specific bodily fluids mentioned here, and activities without exposure to these fluids carry a very low likelihood of HIV transmission.

While transmission of HIV from oral sex is theoretically possible, the risk is very low.3 Although difficult to quantify precisely, the figure lies somewhere between 0% and 0.04% chance of transmission per sexual act.4 Factors that may increase these low risks include ejaculation in the mouth with oral ulcers, bleeding gums or genital sores, or the presence of other sexually transmitted infections (STIs).3

HIV can also be transmitted perinatally, which means it can be passed from an HIV-positive mother to their child during pregnancy, childbirth, or breastfeeding.3 This is an important route of transmission to consider in maternal healthcare and prevention efforts. Anyone can get HIV regardless of sex or gender.


There are several pre-exposure methods available to help prevent HIV transmission during sexual intercourse, including using condoms, knowing your HIV status, and getting tested regularly for other STIs.

Use condoms

How good are condoms at preventing HIV? Condoms are highly effective in preventing HIV and other STIs, although it's important to note that in practice condoms do not prevent HIV 100%, as they can still break during sexual intercourse.8 Both external condoms (condoms for the penis) and internal condoms (also known as vaginal condoms) can be used as a barrier method.

Internal condoms prevent HIV just as well as external condoms, so long as they are both used correctly.9 Internal condoms also provide additional preventative effectiveness to both men and women as they cover the entrance to the vagina and base of the penis; these are areas where STI sores can develop and make it easier for HIV to enter.9

Exploring effective ways on how to prevent HIV transmission to and from others is key when engaging in vaginal and anal sex, particularly if done without the use of condoms.

Note that people who engage in condomless anal sex are more likely to acquire HIV than those who engage in vaginal sex.3 Being the receptive partner (bottom) is also riskier than the insertive partner (top) because the rectal lining is thin and more vulnerable to HIV entering the body.3

Behaviours that might increase exposure and transmission of HIV

The following can be seen as behaviours that might increase exposure and transmission of HIV:6

  • Having condomless anal or vaginal sex when partners do not know their HIV status and/or not using other preventative measures (i.e. PrEP).
  • Having anonymous sex partners, as discussions around HIV prevention, STIs or their own status are unlikely to have taken place. Open communication and mutual consent are essential to allow for a positive experience.
  • Having sex while under the influence of drugs (chemsex) or alcohol as they can lower inhibitions.


Absolutely. Consistently taking HIV medication as prescribed and achieving undetectable levels of the virus ensures that a person living with HIV won't transmit it to others.5 This concept is often summarised as "Undetectable = Untransmittable (U=U),” which aims to destigmatise sexual relationships in people living with HIV.

U=U emphasises that when someone with HIV has an undetectable viral load, there is zero risk of transmitting the virus. This helps reduce stigma and discrimination, promoting a more inclusive and informed view of intimate relationships involving people living with HIV.

HIV prevention methods for serodiscordant couples/encounters

Serodiscordant refers to couples or encounters where one person is HIV-positive, and the other is HIV-negative. In such situations, partners have different HIV statuses. U=U ensures that this practice is totally safe and encouraged. In this way, HIV prevention will look slightly different for each party:

For HIV-positive individuals:

  • Practising safe sex, using condoms, and communicating openly with partners are important preventive measures, particularly if the individual has not yet reached an undetectable viral load. For some people living with HIV this may not be possible.
  • Taking antiretroviral (ARV) medications as prescribed, utilising the treatment as prevention (TasP) strategy. ARVs are a key component of HIV prevention, helping people living with HIV become undetectable, and therefore untransmittable (U=U).5
  • Regular viral load tests inform a person living with HIV whether their viral load is detectable or undetectable. Routine viral load tests not only improve the health of people living with HIV, but also contribute to the prevention of HIV.7

For individuals without HIV:

  • Just like HIV-positive individuals, practising safe sex, and using condoms is also an important preventative measure against HIV.
  • If your partner is not undetectable, PrEP can be used as a preventative medication for those at high risk of HIV, offering an additional layer of protection.
  • However, being in a committed relationship with an HIV-positive individual who remains undetectable would mean preventative measures are not necessary, as per U=U. But note for casual encounters, preventative measures may still be required, as other STIs are also a possibility.

The importance of knowing one’s HIV status

Knowing your status through regular HIV testing is crucial for the prevention of HIV as it enables early diagnosis and timely intervention, reducing the risk of transmission to others and improving health outcomes for those affected.

Choosing to share your HIV status helps to prevent transmission by fostering open communication. When individuals disclose their status, it promotes awareness and understanding among partners and encourages safer practices (i.e. condom use). Talking openly about HIV before potential exposure is important. Normalising and destigmatising these conversations breaks the taboo; this, in turn, contributes to effective prevention efforts.

The importance of STI testing

It is not only the responsibility of people living with HIV to get tested for STIs but also anyone having regular sex. It is important to stress that STIs such as chlamydia, gonorrhoea, syphilis or genital herpes/ulcers increase the chances of acquiring HIV.6,10 For example, an STI can cause a sore or a break in the skin, making it easier for HIV to enter the body compared to intact skin.6 As a result, regular testing for other STIs is as crucial as testing for HIV. You can get tested in various places, like sexual health clinics, centres run by charities, or alternatives, depending on where you reside.

For more information on where and how to get tested, visit the Your Guide to HIV Testing and Diagnosis page.


Besides abstinence, taking pre-exposure prophylaxis (PrEP) is one of the most effective tools we have to prevent HIV. PrEP, a prescribed medication, can be taken before someone may be exposed to HIV (i.e. via sexual contact, injecting drugs or occupational exposure). To be effective, the individual must be HIV-negative when starting PrEP.

When PrEP is taken as advised, it's 99% effective at preventing HIV transmission during sex.10

Note that PrEP is much less effective when it isn't taken as prescribed; PrEP can also be used during pregnancy.11,12

PrEP is recommended for those who:11

  • Have a sexual partner with HIV (especially if the partner has an unknown or detectable viral load).
  • Have not consistently used a condom, or have been diagnosed with a sexually transmitted infection in the past 6 months.
  • Share needles, syringes or other drug equipment, especially if they are sharing with an HIV positive partner.
  • Have been prescribed post-exposure prophylaxis (PEP) but continue unsafe sexual behaviours or have had multiple courses of PEP.

Two forms of PrEP are available: the more commonly used daily oral pill and the long-acting injectable (LAI).13 However, unlike the oral pill, LAI PrEP is not available in every country.12

Individuals who would like to know more about their HIV prevention options should talk to their doctor or sexual health practitioner to discuss whether PrEP is right for them.


Anyone who suspects that they have been exposed to HIV should talk to a healthcare professional as soon as they can. They may recommend an emergency course of post-exposure prophylaxis (PEP), a medicine taken after possible exposure to prevent them from acquiring the virus.14 A course of PEP lasts 28 days, so it is imperative that it is taken daily to be effective.14

Specifically, HIV can be prevented so long as PEP is taken within 72 hours after the exposure.14 PEP may not be effective after this period. However, if you think you might be frequently exposed to HIV, PEP may not be the best option for you. Note that other preventative methods should be used along with PEP, such as the correct and consistent use of condoms, not sharing needles and avoiding uninhibited sexual behaviours.14


  • How can perinatal transmission of HIV be prevented?

    Perinatal transmission occurs when a pregnant person living with HIV passes on the virus to their baby.15 PrEP is recommended for someone who has an HIV-positive partner and is considering getting pregnant.

    Taking HIV medicine (antiretroviral therapy, or ART) during pregnancy and providing preventive medicine to the baby can reduce transmission risk to less than 1%.15 After delivery, using formula or pasteurised donor human milk from a milk bank is advised, especially if the parent has a detectable viral load.15

  • Can lubricant prevent HIV?

    Although lubricants do not directly prevent HIV, they can make sex safer. That is because lubricants reduce the risk of vaginal or anal tears caused by dryness or friction while also preventing the condom from tearing.16 This is why lubricants are particularly important for men who have sex with men (MSM), where there is a greater level of dryness and friction within the anus.17

  • Is there a vaccine for HIV prevention?

    There is currently no existing vaccine for HIV prevention, but researchers are actively working towards its development.18 There were attempts to create an HIV vaccine in 2019 in a large-scale phase 3 clinical trial (Mosaico), but it was deemed to be ineffective and discontinued.19 Scientists are working hard searching for a safe and effective preventative HIV vaccine.18,20

  • Can circumcision prevent HIV?

    Overall, circumcision can help prevent HIV transmission, but it is not as effective as other HIV prevention methods. More effective prevention methods are PrEP and condoms.10,21,25

    Circumcision reduces the chance of acquiring HIV by 50-60% in heterosexual contact with HIV-positive females. However, the protective effect is lower at 23% for men who have sex with men (MSM).21 It is thought immune activation within the cells of the foreskin may contribute to acquiring HIV.22

    So, while circumcision reduces the chances of transmission, it does not fully prevent it. Circumcision offers far less HIV protection than abstinence or proper condom use. It also provides no benefit to women's HIV risk.

  • Is PEP stronger than PrEP?

    Note that PEP and PrEP are two different medications used for different purposes. Whilst PEP is used post-exposure, PrEP is used pre-exposure. Comparing whether PEP is ‘stronger’ than PrEP is not valid, as they function differently and are used in different contexts.

    PEP is a 28-day course of drugs used in emergency situations post-exposure, whereas PrEP can be taken daily, event-based, or as a monthly LAI.14,23 ‘Event-based’ dosing involves taking it before sex and then for two days afterwards.23

    There are two drugs in PrEP, usually combined in a single tablet, and three drugs in PEP (usually the same two in PrEP, plus a third one) – the third drug works differently from the first two.23

  • Can antibiotics prevent HIV after exposure?

    Antibiotics are not suitable for the prevention of HIV as HIV is a virus, not a bacterium.24 Antibiotics are used for bacterial infections, not viral ones.24 However, this question should be discussed with a GP/Nurse/Health provider about options to prevent HIV. Taking PEP instead is one of the most effective ways to prevent HIV after exposure.

  • What are 5 ways of preventing HIV?

    1. Condom use: Consistent and correct use of condoms helps to prevent HIV transmission.
    2. PrEP: Taking PrEP daily or as needed (event-based) before a potential HIV exposure can significantly reduce the risk of acquiring HIV.11
    3. Regular testing: Knowing your HIV status through regular testing (in clinics or at home) allows for early detection, which helps to prevent transmitting HIV to others.
    4. Education and awareness: Promoting awareness, safe-sex practices, and understanding how HIV is transmitted helps prevent the transmission of HIV.
    5. Be conscious of behaviours that might increase exposure and transmission of HIV: At ViiV Healthcare, we strongly support a pro-pleasure and sex-positive mindset. We also think engaging in open communication about sexual desires and boundaries is important, as is being mindful and informed of any potential risks. To find out more, head over to our chemsex page.


  1. Body Fluids That Transmit HIV. CDC. Published 2023. Accessed November 7, 2023.
  2. HIV Transmission. CDC. Published 2023. Accessed November 7, 2023.
  3. Ways HIV Can Be Transmitted. CDC. Published 2023. Accessed November 7, 2023.
  4. Patel P, Borkowf CB, Brooks JT, Lasry A, Lansky A, Mermin J. Estimating per-act HIV transmission risk. AIDS. 2014;28(10):1509-1519. doi:
  5. HIV Treatment as Prevention. CDC. Published 2023. Accessed November 7, 2023.
  6. Detailed STD Facts - HIV/AIDS & STDs. CDC. Published 2023. Accessed November 7, 2023.
  7. Condom Fact Sheet In Brief. CDC. Published 2023. Accessed November 7, 2023.
  8. Hayes R, Watson-Jones D, Celum C, van, Wasserheit JN. Treatment of sexually transmitted infections for HIV prevention: end of the road or new beginning? AIDS. 2010;24(Suppl 4):S15-S26. doi:
  9. UNAIDS Point of View the Female Condom and AIDS UNAIDS Best Practice Collection; 1997.
  10. Pre-Exposure Prophylaxis. Published 2022. Accessed November 8, 2023.
  11. HIV Prevention. Test.HIV.Published 2015. Accessed November 8, 2023.
  12. Deciding to Take PrEP. Published 2023. Accessed November 10, 2023.
  13. What Is Injectable HIV PrEP? CLINICIANS’ QUICK GUIDE TM.
  14. About PEP. Published 2023. Accessed November 10, 2023.
  15. Preventing Perinatal Transmission of HIV | NIH. Published 2023. Accessed November 10, 2023.
  16. HIV Prevention.Test.HIV.Published 2015. Accessed November 10, 2023.
  17. Condom and Lubricant Programming in High HIV Prevalence Countries UNAIDS 2014 | GUIDANCE NOTE.
  18. Infographic—Progress Toward an HIV Vaccine. Published May 17, 2018. Accessed November 9, 2023.
  19. Experimental HIV vaccine regimen safe but ineffective, study finds. National Institutes of Health (NIH). Published January 18, 2023. Accessed November 9, 2023.
  20. Laher F, Bekker LG, Garrett N, Lazarus EM, Gray GE. Review of preventative HIV vaccine clinical trials in South Africa. Archives of Virology. 2020;165(11):2439-2452. doi:
  21. Prodger JL, Kaul R. The biology of how circumcision reduces HIV susceptibility: broader implications for the prevention field. Aids Research and Therapy. 2017;14(1). doi:
  22. Yuan T, Fitzpatrick T, Nai Ying Ko, et al. Circumcision to prevent HIV and other sexually transmitted infections in men who have sex with men: a systematic review and meta-analysis of global data. The Lancet Global Health. 2019;7(4):e436-e447. doi:
  23. What’s the difference between PrEP and PEP for HIV prevention? Published January 13, 2022. Accessed November 9, 2023.
  24. Using antibiotics to prevent STIs. Published May 26, 2023. Accessed November 16, 2023.
  25. Marfatia YS, Pandya I, Mehta K. Condoms: Past, present, and future. Indian journal of sexually transmitted diseases and AIDS. 2015;36(2):133-139. doi:

NP-GBL-HVX-COCO-240003 | January 2024

Reporting of side effects

If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via the Yellow Card Scheme at or search for MHRA Yellowcard in the Google Play or Apple App store. By reporting side effects, you can help provide more information on the safety of this medicine.

If you are from outside the UK, you can report adverse events to GSK/ViiV by selecting your region and market, here.