PrEP: Everything You Need to Know

The emergence of the HIV epidemic in the 1980s marked a turning point in public and sexual health. First identified in the UK in 1981, after years of struggling against an epidemic largely ignored by the general public, in which the first victims, mainly those from the gay community, were ostracised instead of being cared for. For decades, HIV was a deadly infection for which there was no cure, causing the death of hundreds of thousands of people across the globe. As a result, many of those in the communities most affected by the crisis mobilised to join the fight against AIDS.

The arrival of triple combination therapy (three drugs taken in combination, also known as a triple cocktail) in 1996 transformed HIV into a chronic but controllable infection for those with access to treatment. From then on, public health policies haven’t stopped evolving, centring around various prevention strategies and increased screening opportunities, as well as recognising treatment as a preventative tool with new forms of pre-exposure prophylaxis (PrEP).

HIV, or human immunodeficiency virus, is a retrovirus. There are two main strains: HIV-1, the most common, most aggressive and the one responsible for the worldwide HIV pandemic, and HIV-2, less common, mainly limited to West Africa, less virulent, less transmissible and evolves more slowly into AIDS (Inserm, 2024).

HIV is spread in three main ways (Santé Publique France, 2025):

• Sexually — through unprotected sexual encounters involving anal and/or vaginal penetration. Oral-genital sex (fellatio and cunnilingus) present less of a risk, but are not 100% risk-free.
• Through blood — contact with contaminated blood when needle-sharing for intravenous drug use or through accidental jabs (seen in nurses, for example).
• Mother–to-child — if a mother living with HIV is untreated, it is possible for them to pass HIV to the baby during pregnancy, birth or breast-feeding.
  

HIV is a retrovirus that infects immune cells containing the CD4 protein on their surface, principally, although not exclusively, CD4+ T lymphocytes. T lymphocytes are white blood cells that play a crucial role in numerous aspects of the immune response system. HIV enters cells, then multiplying and spreading through the organism.

In the absence of treatment, HIV causes the complete disappearance of CD4 T cells. The evolution and severity of the infection is mainly evaluated through the quantity of CD4 cells left in an organism. A standard amount of CD4 T cells lies somewhere between 500 and 1500/mm3.

The first stage, or the primary infection, usually manifests itself as flu-like symptoms. This is also the point in which the infection is most contagious. This is followed by a chronic asymptomatic phase. The most advanced stage of HIV is acquired immunodeficiency syndrome (AIDS). This can occur between 5 and 10 years after infection if left untreated, although timelines vary from person to person. AIDS is characterised by the appearance of opportunistic infections and diseases, such as various types of cancer, pneumocystis pneumonia, tuberculosis, cerebral toxoplasmosis, esophageal candidiasis, Kaposi’s sarcoma, Non-Hodgkin lymphoma etc.

According to the latest report by UNAIDS, “AIDS, Crisis and the Power to Transform”, it is estimated that 1.3 million people around the world contracted HIV in 2024, that’s 40% less than in 2010 (UNAIDS, 2025).

In 2023, 6,402 people were newly diagnosed with HIV in the UK (National AIDS Trust, 2024). This is an increase from 2022, although said increase may be due to the opt-out testing system for blood-borne viruses implemented in England since April 2022, meaning more people overall are being tested for HIV.

According to the National AIDS Trust (2024), the number of men who have sex with men infected with HIV has diminished overall in recent years, despite a slight uptick in 2022. The majority of those identified as newly diagnosed were heterosexual men and women, and 54% of new diagnoses were people of Black African background.

2022 statistics show that of the 3,292 people identified with late diagnosis, 1,136 (34.5%) of them were diagnosed at a late stage of HIV infection.

With this information in mind, it is important to note that access to treatment (e.g., screening, PrEP etc.) is not the same across the United Kingdom, nor within social groups.

Although declining, these statistics show that HIV remains a public health issue even to this day, as diagnosis is still happening relatively late on. This is why medical preventative tools are crucial in our current handling of HIV and AIDS.

Before we discuss PrEP, it’s also important to talk about the two other complementing prevention strategies: TasP and PET.

TasP (treatment as prevention) is the use of antiretroviral drugs through triple combination therapy to stop HIV transmission. As mentioned earlier, triple therapy is the use of three different medications simultaneously, that aims to stop the virus multiplying within the cells at different points in its cycle.

The term TasP is used when an HIV-positive person (seropositive) who has been on treatment for at least 6 months and has had an undetectable viral load for the last 6 months, is unable to transmit the virus (less than 50 copies of HIV per millilitre of blood) (Sida Info Service, 2025). This is what is known as U=U, undetectable = untransmittable.

This strategy comes from three reputed scientific studies: PARTNER and PARTNER 2, conducted with over 1000 couples with serodifferent (meaning one HIV-positive partner and one HIV-negative partner) couples in 14 different European countries. PARTNER was conducted between 2010 and 2014 with gay couples and heterosexual couples. PARTNER 2 was conducted between 2010 and 2018, exclusively with gay couples. This study did not show one single case of HIV contraction, despite 135,000 instances of unprotected sex (58,000 in PARTNER and 77,000 in PARTNER 2), when the seropositive partner had an undetectable viral load thanks to treatment (Rodger et al., 2016 ; Rodger et al., 2019).

TasP marks an important turning point in the destigmatisation of HIV-positive people, as it shows the effectiveness of treatment as prevention in the fight against AIDS.

Post-exposure treatment, or post-exposure prophylaxis is an emergency treatment that can be prescribed in the case of accidental HIV exposure through blood or sexual contact (unprotected anal and/or vaginal penetration). It’s a form of triple combination therapy that must be started as soon as possible after a high-risk encounter, preferably less than 4 hours after, and at the latest 48 hours after. Exceptionally, this treatment may be started up to 72 hours after the fact, but its efficiency is heavily limited. Treatment lasts 4 weeks. In order to optimise the efficiency of PEP, it is of the utmost importance that you respect the duration, prescribed doses and schedule for the treatment. You can get PEP in sexual health and HIV clinics, but can also be prescribed in Accident and Emergency departments if exposure happens out of hours. It is not normally prescribed by GPs.

Follow-up tests will be done during treatment: a blood test to check for HIV at the start of the four weeks (day 0), a second one at the end (day 28), and a final one after three months in order to confirm the absence of infection.

Follow-up tests will be done during treatment: a blood test to check for HIV at the start of the four weeks (day 0), a second one at the end (day 28), and a final one after three months in order to confirm the absence of infection.

PrEP (pre-exposure prophylaxis) is an innovative prevention strategy for HIV-negative people. It’s a form of medication (containing emtricitabine and tenofovir disoproxil) that is designed to be taken orally. Initially known as Truvada®, nowadays, it is widely accessible in generic formats.

This dual-therapy medication inhibits the reverse transcriptase, an enzyme required by the virus to copy DNA molecules inside the cells. Without this enzyme, the virus is unable to implant itself within an organism upon exposure.

Its efficiency period differs depending on the exposed tissue. Rectal tissue concentration is reached more quickly, with efficiency reached upon 2 to 24 hours of taking. Vaginal tissue concentration takes a lot longer to reach, with 7 days of continuous treatment required to reach optimal protection.

There are two treatment methods available:

• Daily PrEP: a tablet taken at the same time every day to ensure continuous protection. This is highly recommended for those who partake in vaginal sex. Various studies have proved the efficiency of this method: (2007-2010), Partners PrEP (2008-2010), TDF2 (2007-2010), PROUD (2012-2014).
• PrEP on-demand: is one or two tablets taken between 24 and 2 hours before sex. This is recommended for anal sex only. The iPergay study showed the efficiency of this method.
  

Contrary to popular belief, PrEP is not reserved exclusively for gay men. It is prescribed based on an individual’s self-assessment of risk rather than their belonging to a specific group of people. Repeated exposure to unprotected sex, having multiple sexual partners without knowing their HIV status, repeated use of emergency contraception, and a spontaneous request from the individual themselves are all reasons for accessing PrEP.

Although PrEP is truly innovative in preventing HIV infections, it cannot protect you from other STIs.

The decision to use PrEP is a personal one. As with other forms of prevention and contraception, it is important to find the right tools for your personal experience, the ones that will contribute to your overall sexual wellbeing.

PrEP can be prescribed by NHS sexual health clinics. Before being prescribed PrEP, you’ll be asked to do a full STI screening and a blood test for HIV and kidney function.

You have to go for regular check-ups when taking PrEP: HIV testing, STI screening and kidney function tests every three months. This follow-up also provides a regular opportunity for a comprehensive review of sexual health, going beyond HIV alone.

In late 2025, the NHS announced the roll-out of long-acting injections to prevent HIV. The cabotegravir injection, to be administered every two months, will be available for those unable to take PrEP in tablet form. It is backed by robust clinical trials: the HPTN 083 trial (involving men who have sex with men and trans women) and the HPTN 084 trial (involving cisgender women) both demonstrated greater efficacy than daily oral PrEP.

This option is already offered in other countries, such as in France, where Apretude® is available for free.

This new formulation is designed, in particular, to address the compliance issues associated with taking a tablet every day — such as stigma, forgetting to take the tablet, and lifestyle constraints.

There also exists another drug, Lenacapavir, that is injected into the abdomen only twice a year, but it is not yet available for use.

Oral PrEP can cause temporary digestive issues (particularly at the beginning of treatment), and lead to kidney and bone problems (hence the importance of regular check-ups).

Injectable PrEP can cause reactions at the injection site. Clinical data will be better documented over the coming years.

HIV is no longer the fatal condition it once was. A combination of preventive measures — effective treatments (TasP, TPE, PrEP), risk-reduction tools (condoms, dental dams, regular testing) and tailored care — now enables comprehensive and optimal management. The challenge now is to ensure truly equitable access for everyone.