Despite significant advances in HIV treatment, transmission remains a public health concern. In 2022, there were 1.3 million new HIV infections worldwide and 1,888 new diagnoses in Italy, with sexual transmission being the predominant route. Many individuals are still diagnosed late, and a portion of people living with HIV are unaware of their status. Pre-Exposure Prophylaxis (PrEP) has emerged as an effective biomedical strategy to prevent new infections, especially when integrated into comprehensive prevention efforts.

Study Objectives The primary objective of this observational study is to establish a large prospective cohort of individuals using PrEP in Italy. The study aims to assess PrEP's effectiveness, tolerability, adherence, and barriers to long-term use in a real-world setting. These data will be instrumental in guiding future strategic interventions to optimize PrEP management and move toward the goal of zero new HIV infections in Italy.

Primary Objective

• To assess the incidence of new HIV infections among PrEP users in Italy. Secondary Objectives
• Incidence of other sexually transmitted infections (STIs);
• Tolerability of PrEP;
• Psychological and behavioral aspects related to PrEP use;
• Adherence and persistence in care;
• Use of therapies and prophylaxis for STIs during PrEP use. Study Design and Coordination This is a prospective observational study, promoted by Fondazione ICONA in collaboration with clinical centers and community-based organizations. The coordinating enrolling center is INMI "L. Spallanzani" IRCCS in Rome.

Participating Centers:

• 49 university and hospital-based centers across Italy;
• 4 non-clinical checkpoints offering PrEP screening, prescription, and follow-up.

Study Population Adults (≥18 years) who are HIV-negative, sexually active, and considered eligible for PrEP per national or international guidelines, including both new and current PrEP users.

Inclusion Criteria

• Age ≥18 years;
• Negative HIV test at enrollment;
• Willingness to initiate or continue PrEP;
• Informed consent provided. Exclusion Criteria
• HIV infection or strong suspicion of infection;
• Contraindications to PrEP medications; Known allergy to PrEP components; Refusal to comply with study procedures.

The PrIDE study is a national, multicenter, prospective observational cohort aimed at assessing the effectiveness and real-world implementation of HIV pre-exposure prophylaxis (PrEP) in Italy. It collects sociodemographic, clinical, laboratory, behavioral, and quality-of-life data from about 5,000 HIV-negative adults (≥18 years) initiating or already on PrEP, in accordance with Italian and international guidelines.

All 49 university and hospital infectious disease clinics and 4 community-based checkpoints across Italy can participate. Participants are followed every 3-5 months through routine clinical visits, including HIV/STI testing, safety labs, and electronic questionnaires via a dedicated mobile app.

The primary objective is to estimate the incidence of HIV seroconversion, while secondary aims include monitoring sexually transmitted infections, evaluating safety and tolerability, and analyzing adherence, persistence, and behavioral factors. Data are collected in a secure, encrypted eCRF managed by the ICONA Foundation.

The study is coordinated by the National Institute for Infectious Diseases "L. Spallanzani" IRCCS in Rome, will run for at least 10 years, and requires approval from the Ethics Committees of all participating centers.

Inclusion Criteria:

• Age >18 years
• Negative HIV Ab/Ag test (4th generation or higher) at the enrollment visit
• Request and/or willingness to take PrEP, or already on PrEP
• Ability to understand the study procedures and to sign informed consent

Exclusion Criteria:

• Individuals with HIV infection or with strong clinical/epidemiological suspicion of HIV infection
• Individuals with contraindications to the use of medications included in the PrEP regimen (as per the product information)
• Documented allergy to one or more pharmacological components of the proposed PrEP regimen
• Lack of willingness to adhere to the required procedures and follow-up assessments

Prospective enrollment is planned for all individuals taking PrEP in Italy, with the aim of establishing a cohort under active follow-up.

Eligible participants are adults (>18 years old), HIV-negative, and sexually active, who-according to approved national and international guidelines and/or standard clinical practice-are deemed suitable to receive a PrEP prescription or are already undergoing PrEP.