PrEP decreases HIV incidence by nearly 80% in west African men, despite suboptimal adherence


HIV incidence among west African men taking PrEP fell by 79%, when compared to an earlier cohort of men who did not have access to PrEP. This is despite adherence not being optimal for most men, especially among those taking event-driven PrEP. This PrEP demonstration study was conducted in four west African cities by Dr Christian Laurent from the University of Montpellier and colleagues and published in The Lancet HIV.

While overall HIV incidence in west African countries is around 1% in the general population, it is much higher among men who have sex with men (MSM), at approximately 13%. A great deal of stigma and discrimination is directed towards gay and bisexual men, affecting outcomes along the HIV care continuum in west Africa. Côte d’Ivoire, Mali, and Burkina Faso lack legal LGBT equality and protections, while Togo outlaws all same-sex sexual activity. Additionally, many African MSM also have sex with women, thereby contributing to more widespread epidemics. In these contexts, access to PrEP in accessible and safe community-based settings is a crucial factor that could result in decreased HIV incidence in this key population.

The World Health Organization has recommended PrEP for MSM since 2014. These recommendations were updated in 2019 to include event-driven PrEP, also known as the 2:1:1 approach: two pills taken two to 24 hours prior to sex, one taken 24 hours after the first dose, and another taken 48 hours after the first dose.

The study

The current prospective cohort study has been running in four MSM-friendly community-based clinics in Abidjan (Côte d’Ivoire), Bamako (Mali), Lomé (Togo), and Ouagadougou (Burkina Faso) since 2017. It is an extension of an earlier cohort study (which did not include PrEP) that had been in place since 2015 at the same sites, with some men participating in both.


event driven

In relation to pre-exposure prophylaxis (PrEP), this dosing schedule involves taking PrEP just before and after having sex. It is an alternative to daily dosing that is only recommended for people having anal sex, not vaginal sex. A double dose of PrEP should be taken 2-24 hours before anticipated sex, and then, if sex happens, additional pills 24 hours and 48 hours after the double dose. In the event of sex on several days in a row, one pill should be taken each day until 48 hours after the last sexual intercourse.

retention in care

A patient’s regular and ongoing engagement with medical care at a health care facility. 

post-exposure prophylaxis (PEP)

A month-long course of antiretroviral medicines taken after exposure or possible exposure to HIV, to reduce the risk of acquiring HIV.


Having sex without condoms, which used to be called ‘unprotected’ or ‘unsafe’ sex. However, it is now recognised that PrEP and U=U are effective HIV prevention tools, without condoms being required. Nonethless, PrEP and U=U do not protect against other STIs. 

community setting

In the language of healthcare, something that happens in a “community setting” or in “the community” occurs outside of a hospital.

Eligibility to participate included being an HIV-negative adult man who reported anal sex with another man in the previous six months, and any of the following risk criteria: a sexual partner living with HIV not virally suppressed, condomless sex with more than one partner, a prior STI, use of post-exposure prophylaxis (PEP), or requesting PrEP. Men were excluded if they showed any signs of acute HIV infection, any contraindications for PrEP or a hepatitis B infection.

The men were offered a choice between daily and event-driven PrEP (fixed-dose tenofovir disoproxil fumarate 300mg and emtricitabine 200mg), and could switch, stop and restart at any time based on their needs. They were monitored by doctors and peer educators at baseline (first PrEP delivery), at months one and three and then every three months thereafter. They could also attend unscheduled visits. At each visit, participants underwent a medical interview and examination (including providing self-reported PrEP adherence data), HIV testing, STI screening and symptomatic treatment, and were provided with psychosocial support, condoms, lubricant and a PrEP refill. Peer educators contacted participants if they were 15 days late for a scheduled visit.


During a median follow-up time of 17.6 months from 2017 to 2020, 598 MSM with a median age of 24.6 participated in the study – 41% from Mali and approximately 20% per country from the remaining three countries. The majority of participants (58%) identified as bisexual and 37% as gay. Most identified as cisgender (60%), while 29% identified equally with both genders and 11% as transgender. Interestingly, nearly half reported having a wife or girlfriend (47%).

The vast majority reported having one male sexual partner, with 48% reporting one to four sex acts with a stable male partner and 42% reporting this amount with a casual male partner in the past month. Consistent condom use in the past three months was reported by less than half of the sample (44%). All the men viewed themselves as at a low risk of acquiring HIV, either from a stable or casual partner. However, a high number had previously been tested for HIV (81%).

At baseline most participants in all four countries chose event-driven PrEP. Overall, around three-quarters of men chose event-driven PrEP (74%). More men changed from daily to event-driven PrEP (42%) than vice versa (13%) during the course of the study. Event-driven PrEP tended to be less commonly used by participants living in Burkina Faso and Togo, older men, those with a wife or girlfriend and those with a high number of male sexual partners. A total of 6% discontinued PrEP at least once.

In terms of self-reported adherence to PrEP at the time of the most recent sex act, it was reported as optimal 41% of the time for event-driven and 71% of the time for daily regimens. PrEP had not been used 31% of the time on those taking event-driven PrEP and 18% of the time for those on daily PrEP. Optimal adherence was significantly lower with event-driven than PrEP.

There was an overall HIV incidence of 2.3% per year (95% CI 1.3-3.7), with 17 men getting HIV during the follow-up period. This was lower than the previous cohort of men, who received other HIV prevention services but did not receive PrEP – they had an incidence of 10% per year (95% CI 8-12.5). This represented a 79% decrease in the HIV incidence when comparing these two groups. Of those who acquired HIV, 15 were on event-driven PrEP, one was on daily PrEP, and one had discontinued PrEP some time ago. While HIV incidence was 2.7%, 0.6% and 6.1% per year for event-driven, daily and no PrEP respectively, the difference between event-driven and daily PrEP was not statistically significant. Of 15 participants with HIV and genotyping information, only one had resistance to emtricitabine, with none having resistance to tenofovir.

There was no evidence of increased sexual risk behaviour, with the average number of male sex partners in the previous three months and the number of sex acts with casual male partners in the previous month instead decreasing over the follow-up period. The proportion of those having condomless sex did not change significantly over time. The prevalence of gonorrhoea, chlamydia and syphilis remained stable over time.

A quarter of men were lost to follow-up – half of these within the first six months, highlighting the challenges with retention in African settings.


“The results from this multicountry demonstration study on PrEP for MSM in west Africa are encouraging. PrEP availability helped prevent HIV infection and did not lead to an increase in risky sexual behaviours or other STIs. In addition, HIV drug resistance was rare. PrEP should be urgently implemented in HIV prevention programmes in west Africa. However, retention in care and adherence to PrEP require special attention so that PrEP can reach its full prevention potential,” the authors conclude.


Laurent, C et al. HIV pre-exposure prophylaxis for men who have sex with men in west Africa: a multicountry demonstration study. The Lancet HIV, published online 25 May 2021.

Correction: This article was amended on 5 July 2021 to clarify that in the event-driven regimen, the second dose should be taken 24 hours after the first dose, rather than 24 hours after sex.