PrEP Impact FAQs



If you need PrEP and are not on the trial, please ask your clinic if they have PrEP available through the new commissioned service.

For other alternative ways to access PrEP in the UK see  

The PrEP Impact Trial has been running in sexual health clinics across England since September 2017. For any questions regarding the trial and study drug please first refer to the Participant Information Sheet.

Since the start of the study there have been changes to the trial sponsorship, increases to the number of study places, and updates to the trial protocol. The FAQs below have been updated to reflect the current status of the trial; questions that have been archived can still be accessed here

Trial Information & Design

What is HIV PrEP?

Pre-exposure prophylaxis, or PrEP, is medication taken by an HIV negative person, who is at substantial risk of HIV infection so as to reduce their risk of acquiring HIV. This involves taking PrEP as instructed, before any exposures that might put them at high risk of getting HIV. The single-tablet PrEP drug contains two medicines (tenofovir and emtricitabine) which are also used to treat HIV infection.

What is the PrEP Impact Trial?

The PrEP Impact Trial aims to answer key questions about the use of PrEP in England. The trial was announced by NHS England and Public Health England in a joint statement on 4th December 2016. The trial is planned to last three years. It initially aimed to recruit 10,000 participants at high risk of acquiring HIV; this has now been increased to 26,000.

Whilst the efficacy of PrEP has been clearly established in multiple trials across the world, including the PROUD trial that was conducted in England, the relatively small number of people enrolled in that trial meant that some key questions about large-scale use of PrEP in England remained. The PrEP Impact Trial aims to address the outstanding questions about eligibility, uptake and length of use.

The trial is a health technology assessment of PrEP and its implementation, that is, it aims to answer the key questions under real world conditions and at sufficient scale. In addition, the new trial will assess the impact of PrEP on the overall number of new HIV diagnoses and sexually transmitted infections. The results will inform service commissioners (funders) on how to deliver a PrEP programme in the future, when PrEP will be made available as part of routine care in sexual health services.

Why is a trial needed?

The trial is designed to address major questions that will determine effective future implementation of PrEP on a large scale. These questions are:

  • What proportion of people attending sexual health clinics will be at high risk and eligible for PrEP?
  • What proportion of people who are offered PrEP will accept it?
  • What is the length of PrEP use in those who accept the offer?
  • What is the impact on HIV incidence in the population?
  • What is the impact on STI incidence in the population?

How many people are on the trial?

At the start of the trial in 2017 there were 10,000 participant places available across England; this target was based on the best available evidence at the time regarding who was eligible for PrEP amongst sexual health clinic attendees. In June 2018 an additional 3,000 places were added to the trial to adjust for the initial high recruitment observed across sites.

In early 2019 further review of study recruitment prompted a recommendation that the trial size be increased to 26,000 participants in total; this was agreed to by the Programme Oversight Board. Recruitment across the study has exceeded initial expectations and in order to properly answer the study objectives it was considered necessary to increase the number of places available.

Does the trial team have an idea of the number of people they expect to recruit from each area, and how are places allocated?

Yes, these estimates are based on best available surveillance data of clinic attendance and will be tested during the trial.

It is one of the trial objectives to measure clinic throughput and in different regions; as such uptake across clinics is monitored as part of routine trial data collection. This information will be used to inform on patterns of use in updates to the Trial Steering Committee and PrEP Programme Oversight Board that is jointly chaired by Public Health England (PHE) and NHS England.

Who has been engaged in planning this trial and have community organisations been involved?

The planning of the trial has been led by PHE and NHS England. The trial is overseen by the PrEP Programme Oversight Board that is jointly chaired by PHE and NHS England. The Programme Oversight Board was convened in January 2017 and now has representation from the Association of Directors of Public Health, Local Government Association, the English HIV and Sexual Health Commissioners Group (EHSHCG) and the community (there are three lay-representative members).

The trial team actively engaged with clinicians and community groups in planning the trial. There were a series of meetings, convened by PHE, of the Task and Finish Group and Community Advisory Board. The Community Advisory Board was comprised of community representatives from across England and co- chaired by Public Health England and the National LGBT Partnership.

The Community Advisory Board was originally designed to achieve participation before the trial and so was temporarily disbanded, but has since been re-formed to provide advice to the Trial Management Group as the study continues. Membership includes members from the following groups:

Africa Advocacy Foundation (AAF)

African Eye Trust

African Health Policy Network (AHPN)

BHA (Black Health Agency) for equality in health and social care

cliniQ CIC

GMFA – the gay man’s health charity


LGBT Foundation

London School of Hygiene and Tropical Medicine

NAM (National AIDS Manual)

National Aids Trust (NAT)

National Ugly Mugs

NAZ Project

Porn for PrEP UK

Positively UK


Sophia Forum

Spectra CIC and GMI Partnership

Terrence Higgins Trust (THT)

UK Community Advisory Board

Yorkshire MESMAC

Has the trial received ethical approval?

The Trial received ethical approval in early August 2017. Further approvals were given in July 2018, and February 2019 for the increases to the number of places.

The reference numbers for the PrEP Impact Trial are: REC reference 17/LO/1134; IRAS ID 228166.

What happened to St Stephen’s Clinical Research?

In July 2018 the legal responsibility and management of the trial moved from St. Stephen’s AIDS Trust (SSAT) and St. Stephen’s Clinical Research (SSCR) to Chelsea and Westminster NHS Foundation Trust. This was due to the planned closure of SSAT/SSCR.

This change of sponsorship had no impact on current or potential trial participants at trial sites. Amendments to the study were administrative between SSAT/SSCR and Chelsea and Westminster. If already enrolled on the trial, all participants were able to continue to access PrEP and attend their follow-up visits.

You can read about the change of sponsorship here.

Where does the trial take place?

The trial is conducted in sexual health clinics across England. All specialised genitourinary medicine (GUM) clinics (i.e. level 3 sexual health clinics) have been invited to participate in the trial.

The PrEP Impact trial website includes a list of trial sites that are enrolling participants. This is updated regularly to reflect clinic status (open/paused) in relation to places available for gay and bisexual men having sex with men (MSM) and for women and other people.

Trial sites are required to meet a number of criteria to be able to participate in the trial, including:

  • Adequate capacity to deliver the sexually transmitted infections (STI) and HIV testing
  • Systems in place to prescribe and dispense PrEP
  • Systems in place to record and report trial data in a timely fashion

When did the trial start and how long will it last?

The trial started enrolling participants in October 2017 and is intended to continue recruiting new participants to mid July 2020. Different clinics have opened to participants at different times. As the majority of sexual health clinics are taking part, you should not need to travel far to access the trial and you can receive all your sexual health care in the same place.

Joining the Trial

How can I find out more about the PrEP Impact trial?

The best way to discuss PrEP and find out more about the trial is to visit your local participating clinic.

Further information can be found in the Trial Protocol and the Participant Information Sheet, both of which can be found on this website.

The Prepster website ( also contains information on accessing PrEP in England.

How are individuals able to join the trial?

PrEP will be offered to individuals attending participating genitourinary medicine (GUM) clinics, who meet the trial criteria and consent to participate.

If you wish to join the trial, the best way is to contact one of the participating clinics. You can see a list and map of participating sites at:

What are the eligibility criteria?

The eligibility criteria for the trial are based on criteria published by NHS England as part of the consultation on the draft commissioning policy proposal in August 2016. They were developed in discussion with clinical colleagues who participated in the Public Health England (PHE) PrEP Task and Finish Group and community representatives who participated in the Community Advisory Board convened by PHE.

PrEP will is offered to individuals considered to be at high risk of HIV acquisition. Three groups of individuals have been identified and the eligibility criteria have been set to match this.

a) HIV-negative MSM and trans women who report condomless sex in the previous 6 months and on-going condomless sex.

b) HIV-negative individuals having condomless sex with partners who are HIV positive, unless the partner has been on ART for at least 6 months and their plasma viral load is <200 copies/mL.

c) HIV-negative individuals who are clinically assessed and considered to be at similar high risk of HIV acquisition as those described in category B above.

For example, this means that any of the following persons may be eligible for PrEP:

  • A woman or man reporting sex without a condom with partner(s) from countries with a high prevalence of HIV and intending to continue doing so.
  • A female sex worker reporting inconsistent use of condoms with clients from countries with high prevalence of HIV.
Trial participants must be aged 16 years or over. Whilst there may be individuals under the age of 16 at high risk of acquiring HIV, the ethics of research mean that it is not possible to include these participants. If you are under 16 and think you might be at risk please attend your local sexual health/GUM clinic or speak to your GP or a trusted adult.

Are all eligible populations able to participate in the trial?

Any person assessed as being at high risk of acquiring HIV by meeting the eligibility criteria outlined above may join the trial. In order to reach a significant proportion of those at highest risk of HIV acquisition, and in response to the higher than expected levels of enrolment to the trial, the number of places was increased to 13,000 in 2018, and then to 26,000 places in 2019.

Recruitment is regularly monitored by the Trial Management Group, including which population groups are being recruited. Community groups, through representation on the Community Advisory Board, Trial Management Group, and Trial Steering Committee are kept informed of recruitment demographics and numbers.

If certain population groups at equivalent high risk of HIV are under-represented in recruitment, we work through the CAB to inform and encourage those under-represented groups to enrol in the trial.

Does a person’s nationality or immigration status affect whether they are able to participate in the trial?

No, as long as they are resident in England. Unlike some other NHS services, there are no immigration or nationality restrictions on accessing services provided by GUM clinics in England. This is because of the wider public health benefit of everyone being able to freely access sexual health treatment and prevention services and advice. The trial follows the same principles.

Will a proportion of participants on the trial be given a placebo?

No. Everybody who takes part in the trial will be given PrEP. A placebo (dummy pill, with no therapeutic effects) is not required as this trial is not about whether the drug is effective – there is already sound evidence to show that it works.

What is the suggested pathway for those who enrol in the trial?

People attending a clinic, who are part of groups at high HIV risk, will be asked about their individual circumstances to assess their potential risk. Those who are eligible for, and accept the offer of PrEP will initially be prescribed PrEP for three months, to be taken either every day or event based, depending on their circumstances. . Event based dosing is when PrEP is taken before and after having sex.

For new PrEP users (and those who have never taken PEP, post exposure prophylaxis) they will have a one month follow-up to check for any difficulties or problems they may be experiencing, and to answer any questions. This can be by phone, email, or in person if required. After the first month, and for existing PrEP users (and past PEP users), participants will be advised to return to the clinic at three month intervals, to test for HIV and screen for other STIs, and to check they wish to continue to use PrEP.

All clinical care provided to participants is in line with clinical guidance from BHIVA/BASHH for PrEP []. Participants are offered PrEP as part of an active risk reduction intervention, including health education and safer sex promotion, to reduce and modify high risk behaviour. This may include the provision of free condoms, behaviour change interventions, other biomedical interventions such as post-exposure prophylaxis where relevant, substance misuse interventions, the diagnosis and treatment of sexually transmitted infections (STIs), and regular HIV testing.

Participant Questions

Where do I find information about the trial and the study drug?

For any questions regarding the trial and study drug please first refer to the Participant Information Sheet:

Do I have to visit the same clinic throughout the whole trial, or can I enrol at more than one?

It is important that you only enrol at one clinic. If you sign up at more than one, you will be taking a place on the trial that could have gone to someone else. It could also jeopardise the trial being able to capture all the information it needs to answer key questions.

If you need to transfer to another clinic during the trial (for example, if you move to a new town or city) then you will need to speak to your original trial clinic and advise them of your plans. At your first visit to the new clinic you will need to provide your original trial ID (if you do not know this, contact your original clinic and they can provide the number). You will be issued a new trial ID and registered as a participant at the new site. We recommend you take a photo of your consent form and trial ID and keep it on your phone in case you need it in the future.

What happens if I join the trial and then no longer need or want to take PrEP?

Any trial participant may stop taking PrEP without withdrawing from the trial, and then start again at a later date provided they again meet the eligibility criteria.

Deciding when to stop or restart PrEP should be discussed with a clinician at your trial clinic.

You may withdraw from the trial at any time for whatever reason; you will need to inform the clinic where you are registered.

Where can I learn more about taking PrEP, possible side effects, dosing, etc?

You can also see the official product information here:

The Prepster website ( also contains information.

I didn’t get on the trial, what do I do now?

In February 2019 the trial received ethics approval on an amendment to add an additional 13,000 places. These are currently being rolled out at participating sites across England. The list of clinics open to recruitment is being updated regularly:

The i-base leaflet ‘UK guide to PrEP’ includes information on how to access PrEP in the UK:

The Mags Portman PrEP Access Fund supports people with no income or in receipt of benefits to access PrEP