Results of Impact trial, show that HIV pre-exposure prophylaxis (PrEP) is highly effective in preventing HIV acquisition
 

Source: The Lancet HIV, Dec 2023

The results of the Impact Trial, one of the most extensive studies of HIV pre-exposure prophylaxis (PrEP) to date, have been published in the Lancet HIV.

The study, a prospective, open-label, single-arm, multicentre trial, was funded by the NHS. It was conducted at 157 centres across England between Oct 13, 2017, and July 12, 2020, and enrolled more than 24,000 participants over the three years. 

In real-life settings, the use of PrEP reduced the chances of getting HIV by around 86%, allowing for differences in correct use. (earlier clinical trials suggested the medication is 99% effective.)

The trial participants belonged to one of three population groups:

“HIV-negative men (cisgender and transgender) and transgender women reporting condomless anal intercourse with men in the previous 3 months and likely to repeat this activity in the subsequent 3 months; HIV-negative partners reporting condomless sex with an HIV-positive person who was not known to be on antiretroviral therapy (ART) and who was not adequately virally suppressed (<200 copies per mL for 6 months or more); and HIV-negative people considered to be at equivalent HIV risk to those in the second group.”¹
 

According to the researchers Sullivan and Saunders et al., the data support…

” earlier evidence that PrEP is highly effective; incident HIV infections were rare and almost all occurred in the context of having discontinued PrEP. Although STI incidence was high, this was concentrated among a minority of participants and was more likely among those with a history of STIs than among those without."¹
 

They further report that the need was higher than initially estimated by the expert stakeholder group, and the high proportion of follow-up time protected by PrEP suggests that the need for protection persisted throughout trial participation for most participants.
 

The results are significant, signalling that PrEP may be an essential step towards the elimination of HIV transmission when used in combination with HIV prevention. To be effective in a real-world setting, however, more needs to be done to optimise PrEP delivery to those who would benefit the most.