From a contested study on U=U to a disappointing gonorrhoea vaccine trial and the ongoing global PrEP crisis, HIV prevention was a key topic at this year's Conference on Retroviruses and Opportunistic Infections (CROI 2026) in Denver. Here are five highlights.
A study from Rakai in Uganda calculated a small but quantifiable risk of HIV transmission at viral loads between 200 and 1000. This appears to challenge the threshold used in 'Undetectable equals Untransmittable' (U=U) messaging. The findings generated considerable debate, with other researchers questioning the assumptions underlying the estimates and whether advice clinicians give to people living with HIV should change.
A randomised trial of the 4CMenB vaccine in gay and bisexual men found it was no more effective than a placebo at preventing gonorrhoea – a result described by the researchers as "unexpected and somewhat disappointing, but very clear." Observational studies had previously suggested the vaccine might prevent a third to nearly half of infections, and the UK has already started to make it available. However, the results should not be generalised to cisgender women, for whom the route of infection and risk of complications are different.
Even before US funding cuts, PrEP coverage was far too low in most countries to make a meaningful dent in HIV incidence – and the cuts have made things much worse. Around 42 people need to be on PrEP to prevent one HIV infection per year – a benchmark that only Australia, Denmark, Norway and the UK were close to achieving by the end of 2024. Even countries with large numbers of PrEP users were far off the target – the US had 15 PrEP users for every one new infection and South Africa had five people on PrEP for every new infection. In Africa, the PEPFAR cuts have since reduced PrEP numbers drastically – by 28% in South Africa, by 58% in Zambia and 98% in Nigeria.
HIV incidence among transgender women in the US remains high, with stark disparities by race and ethnicity and strong links to poverty, homelessness and lack of health insurance. The findings from a longitudinal cohort, which followed over 2500 trans women across the US for two years, underline the need for tailored, gender-affirming prevention – including wider access to long-acting injectable PrEP, used by only 4% of PrEP users in the study.
The final results of an eight-year French study confirmed that both daily and on-demand oral PrEP are safe and effective over the long term. Most of the 3209 participants were gay or bisexual cisgender men and at any given point roughly half were taking daily PrEP and half event-driven dosing – though individuals switched frequently between the two. The results reinforce the importance of offering people a genuine choice of PrEP regimen.
