Welcome to the PrEP Impact Trial website

PrEP is a way for people to reduce their risk of acquiring HIV.


The PrEP Impact Trial was set up to recruit 26,000 participants who are at a high risk of HIV infection in England. 


Message for Impact trial participants

On behalf of Chelsea and Westminster Hospital NHS Foundation Trust and Public Health England, we would like to thank you for your participation in the PrEP Impact Trial.  Recruitment to the trial closed in July 2020.


The PrEP Impact trial was due to end on 12th October 2020, however it has been extended for a short period due to COVID-19 to enable all participants to attend their final trial visit.


If you have not attended your clinic since 13th July please do so as soon as possible.

If you have had an online test since 13th July please let your clinic know so they can confirm you have had your final screen.


It is important you attend for your final trial visit to ensure all your trial data contributes to the final trial results which will be used to help design and deliver the routine supply of PrEP in England.


It will also ensure you obtain an ongoing supply of PrEP if you need it. This can be via the routine service if it has started at your clinic, or if not via the interim supply. The interim supply of PrEP is provided by NHS England and is available for all trial participants (even if you haven’t attended recently) until routine PrEP is locally available.


You can find more end of trial information here



What is PrEP?

PrEP (HIV Pre-exposure Prophylaxis) is a medicine for HIV negative people, is taken before sex, so it is pre-exposure. Prophylaxis means to prevent infection – in this case HIV. It can reduce the risk of acquiring HIV when taken as instructed. 


PrEP is made up of two drugs, Tenofovir and Emtricitabine. These drugs are known as antiretroviral medicines and have been used as part of HIV treatment for many years. You may know this medicine by its brand name, Truvada, however there are generic forms of the drug with the same active ingredients.

Who would benefit from PrEP?

You could benefit from PrEP if you are considered to be at high risk of HIV. PrEP can be used as a way to reduce your risk of HIV if you are HIV negative and don’t always use condoms. 


Other factors related to a higher risk of HIV are:

  • A recent STI (especially rectal infection such as syphilis, Hepatitis C or Lymphogranuloma venerum ) 

  • Use of PEP (post exposure prophylaxis)

  • Using some recreational drugs (crystal meth amphetamine, mephedrone or GHB/GBL) - also known as Chemsex


PrEP is not a vaccine and only provides protection from HIV so long as you continue to take it as prescribed. It is important to remember that PrEP will not protect you from acquiring other STIs. This is an important advantage of using condoms.

© 2017 PrEP Impact Trial