Pre-exposure prophylaxis (PrEP)

Key points

  • PrEP is highly effective in preventing the transmission of HIV during sex.
  • There are several different forms of PrEP, including pills, injections and a vaginal ring.
  • For PrEP to work well, it’s important to take it or use it consistently, as directed by your healthcare provider.
  • While PrEP can prevent HIV, it does not protect against other sexually transmitted infections or pregnancy.

PrEP stand for pre-exposure prophylaxis. This means it prevents you from getting HIV by taking anti-HIV drugs. PrEP allows you to have the sex you want without the fear of contracting HIV.

The anti-HIV drugs in PrEP stop HIV from entering your cells and replicating. This prevents HIV from establishing itself and stops you from acquiring HIV.

PrEP options

There are several different types of PrEP:

  • The most widely used type of PrEP is a tablet which contains two anti-HIV drugs, tenofovir disoproxil and emtricitabine. This is sometimes known as Truvada. You need to take this tablet every day or take several doses before and after sex to make sure that the drugs maintain high levels in your blood to prevent HIV infection.
  • An alternative PrEP tablet contains tenofovir alafenamide and emtricitabine. This is taken daily and its brand name is Descovy. If you have concerns about your kidney or bone health, this may be more suitable than the other pill.
  • Cabotegravir is a long-acting form of PrEP, taken by injection once every two months. Its brand name is Apretude.
  • Lenacapavir is another long-acting form of PrEP, taken by injection once every six months. Early reports from lenacapavir research are extremely promising, but lenacapavir is not yet available as PrEP.
  • The dapivirine vaginal ring is placed in the vagina and provides protection over the course of a month.

Would PrEP be right for you?

PrEP could be helpful if the sex you are having is not always as safe as you would like it to be. If it is sometimes difficult to use condoms or to be sure of your partner’s HIV status, PrEP could make the sex safer. If it’s likely that some of your sexual partners have HIV without realising it, then PrEP could help protect your health.

People are not expected to take PrEP forever. PrEP is most likely to be useful for a period of months or years when the risk of HIV is greatest. If you no longer feel at risk, you can discuss stopping PrEP with your healthcare provider. You’ll be able to re-start it later.

Susan Cole, Matthew Hodson and Mercy Shibemba talk about the different forms of PrEP available.

While PrEP provides protection against HIV, it does not protect against other sexually transmitted infections or prevent pregnancy. Condoms can provide protection against gonorrhoea, chlamydia, syphilis, hepatitis C and unwanted pregnancy.

PrEP isn’t the right choice for everyone. People who are able to consistently use condoms and other HIV prevention strategies don’t need PrEP.

If your partners definitely don’t have HIV, then PrEP isn’t needed. And if you have a partner who is living with HIV, taking HIV treatment and has an undetectable viral load, there is no risk of HIV transmission anyway. This is also called U=U.

Taking PrEP

Ideally, PrEP should be taken under medical supervision. This is because there are important things to consider before starting PrEP. You need to take an HIV test to check your HIV status. This is to ensure you don’t have HIV before you start taking PrEP.

It’s also recommended to take tests for sexually transmitted infections and pregnancy. If you are planning to use PrEP pills, you should also have tests for your kidney function and the hepatitis B virus. Healthcare providers may ask you some questions about your sexual behaviour and sexual partners before prescribing PrEP.

For PrEP to work, it needs to be taken correctly. This means having enough PrEP in your body at the times when you need protection. If you are taking pills, an occasional forgotten dose will not make PrEP ineffective. But for people who cannot adhere to their treatment and miss pills regularly, PrEP may not work. If you are taking injections, it is very important to attend your clinic as scheduled and receive the injections on time.

While taking PrEP, you will need regular clinic appointments to check for side effects and to repeat HIV testing, as well as for advice and support.

Is PrEP available?

Services which provide HIV testing, treatment for sexually transmitted infections or treatment for HIV may also provide PrEP – or have information on local services which do.

Not all types of PrEP are available in all countries. The most widely used type of PrEP is the tablet containing tenofovir disoproxil / emtricitabine (Truvada) and this is available in many countries. The other PrEP pill, tenofovir alafenamide / emtricitabine (Descovy), is available in a limited number of high-income countries.

At the time of writing, cabotegravir injections (Apretude) had been approved by drug regulators in 19 countries in all parts of the world, plus the European Union. Lenacapavir injections are not yet available anywhere. The vaginal ring is only available in some African countries.

You can check the PrEPWatch website to see which types of PrEP are approved for use in your country. But bear in mind that while drug regulators in your country may have approved a specific type of PrEP, it might not yet be available in clinics and local services. This is often because health organisations still need to make decisions on funding and reimbursement.

Which PrEP option would be right for you?

PrEP pills containing tenofovir disoproxil and emtricitabine (sometimes known as Truvada) are the most widely used and best studied type of PrEP. They are inexpensive and work well for most people.

However, if it would be difficult for you to take pills regularly without missing doses, then a long-acting form of PrEP might be a better option. If you would be able to stick to clinic appointments, then you could try PrEP injections. Or you may be able to use the vaginal ring – you insert it yourself and it stays in for a month at a time.

If you have concerns about your kidney or bone health, or if you are under the age of 18 (a critical time for bone growth), then PrEP pills containing tenofovir disoproxil and emtricitabine may not be the best option. One of the other types of PrEP might be more suitable.

If you are pregnant, breastfeeding or trying to become pregnant, research suggests that tenofovir disoproxil / emtricitabine pills and the dapivirine vaginal ring are safe. We don’t yet have enough information on the other types of PrEP in these situations.


pre-exposure prophylaxis (PrEP)

Antiretroviral drugs used by a person who does not have HIV to be taken before possible exposure to HIV in order to reduce the risk of acquiring HIV infection. PrEP may either be taken daily or according to an ‘event based’ or ‘on demand’ regimen. 

vaginal ring

A device that is worn inside the vagina for a month at a time, which women can insert and remove themselves. A vaginal ring for HIV prevention that slowly releases the antiretroviral drug dapivirine is being developed.


How well something works (in real life conditions). See also 'efficacy'.

sexually transmitted infections (STIs)

Although HIV can be sexually transmitted, the term is most often used to refer to chlamydia, gonorrhoea, syphilis, herpes, scabies, trichomonas vaginalis, etc.


In pharmacology, a medication which maintains its effects over a long period of time, such as an injection or implant.

People who have hepatitis B can take PrEP, but as one of the drugs in PrEP pills (tenofovir) is also active against hepatitis B, your doctor will need to take this into account. If you have hepatitis B and want to take a break from PrEP pills, you should discuss with your doctor how to safely stop taking them. This is not an issue with any of the other types of PrEP.

If you are a cisgender woman or need protection during receptive vaginal sex, PrEP pills containing tenofovir alafenamide and emtricitabine (Descovy) are not recommended. So far, research on how well they work has only been completed with gay and bisexual men and transgender women.

In terms of which type of PrEP is most effective in preventing HIV infection, studies show that PrEP pills and injections are both extremely effective when they are taken consistently, as prescribed. If you are comfortable taking pills and will remember to take them every day, PrEP pills are likely to work very well for you. Nonetheless, in studies, the fewest HIV infections were in people taking injectable PrEP – perhaps because it was more difficult to miss doses.

On the other hand, in studies so far, the dapivirine vaginal ring has provided a lower level of protection than other types of PrEP. It’s also important to bear in mind that the ring only protects against HIV during vaginal sex. It does not provide protection during anal sex.

There are specific pages on this website for each type of PrEP. They provide detailed information about how to start and stop using it, what to do if you miss a dose, required tests before starting PrEP, checkups while taking PrEP, side effects, drug interactions, drug resistance, using PrEP during pregnancy, which countries it is available in and how effective it is.

Click on the links to find out more about:


Image credits: Kuboo/ / megaflopp/ / PrEP Emtricitabine/Tenofovir (Generic Truvada) PrEP Treatment Image 11. Image by Doctor 4U. Available at under a Creative Commons licence CC BY 2.0 / Vaginal ring. Image by NIAID. Available at under a Creative Commons licence CC BY 2.0.


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