The study, published in The Lancet Regional Health – Europe, was led by Dr Juan Ambrosioni, a specialist at the HIV-AIDS Unit of Clínic-IDIBAPS.
A study involving nearly 20,000 PrEP users in Spain
The SCOPE study analysed nearly 20,000 PrEP users from its implementation in Spain in 2019 until March 2025. The study was conducted across 12 centres in Catalonia, the Community of Madrid, Andalusia and Galicia.
During this period, 53 new HIV diagnoses (seroconversions) were detected, a very low figure in relation to the total number of people using this preventive strategy. The results reinforce the high effectiveness of PrEP as a preventive tool against HIV when used appropriately and continuously.
In which situations did HIV infections occur?
The study found that most cases involved young cisgender men who have sex with men. Other sexually transmitted infections and practices associated with increased vulnerability, such as drug use in a sexual context (chemsex), were frequently present. More than 70% of those diagnosed had interrupted PrEP at some point, and nearly half were not using it continuously in the period prior to diagnosis.
In addition, a relevant proportion of cases showed resistance mutations associated with some of the drugs used in PrEP. According to the authors, these findings highlight the importance of carefully ruling out acute HIV infection before initiating PrEP and of performing resistance testing in new diagnoses, as some of these drugs are also part of commonly used antiretroviral treatments.
Despite this, most of the individuals diagnosed started antiretroviral treatment early and achieved adequate virological control during follow-up, with undetectable levels of virus in the blood.
New strategies to strengthen HIV prevention
The researchers note that although the observed incidence was very low, the results should be interpreted in the context of the inherent limitations of observational studies. They also stress that PrEP remains a key strategy to reduce new HIV infections in Spain, while underlining the need to strengthen support and strategies that promote continuity and adherence to preventive treatment.
In this regard, the authors point out that the recent approval in Spain of long-acting injectable PrEP could represent a particularly useful preventive alternative for individuals who have difficulties maintaining a continuous oral regimen.
The study results provide relevant information to optimise prevention programmes and public health strategies against HIV.
The study was funded by the Carlos III Health Institute (ISCIII) and co-funded by the European Union, within the framework of project PI23/00355.
Study reference:
Vera M, Álvarez-López P, Tato H et al. Incidence and Clinical, Virological, and Resistance Characteristics of HIV Infections Among pre-Exposure Prophylaxis Users in Spain (SCOPE Study): A Multicentre Prospective and Retrospective Cohort Study. The Lancet Regional Health – Europe, 2026; 66
