HIV risk messaging and medical mistrust in the era of Undetectable=Untransmittable: Psychosocial and Behavioral Implications among Black, Latino/a/e/x, and Multiracial Sexual and Gender Minorities - Black, Latin American, and Multiracial individuals are disproportionately impacted by HIV. One impact is access to health resources, including HIV knowledge. Knowledge about Undetectable=Untransmittable (U=U), the scientific conclusion that people living with HIV who have a sustained undetectable viral load cannot sexually transmit HIV to their sexual partners, has been associated with reduced HIV stigma and increased HIV testing. However, many people remain skeptical of U=U, in part due to unclear and inaccurate messaging about U=U from trusted sources. Ensuring that messaging about HIV transmission risk is accurate, acceptable, and credible may prove to be a recurrent challenge as knowledge about transmission risk continues to evolve. A 2023 review of evidence indicated that people living with HIV who have a suppressed but detectable viral load (200-1000 copies/mL) have “almost zero” risk of transmitting HIV to their sexual partners (“Almost U=Almost U”; aU=aU), prompting the World Health Organization (WHO) to recommend disseminating this new information. Integrating aU=aU into HIV transmission risk messaging may complicate understanding of U=U and undermine U=U belief. Despite the WHO’s call to disseminate the aU=aU message, no research to date has examined its potential impact. This proposed cross-sectional survey-based study aims to evaluate the effect of messaging about aU=aU on HIV transmission beliefs using a pre/post design with 2,000 Black, Latin American, and Multiracial individuals. A second aim is to examine associations between various demographic and psychosocial factors with (a) perceptions of the message (e.g., acceptability, credibility) and (b) the anticipated impact of the message on psychosocial health (e.g., HIV stigma) and health behavior (e.g., HIV testing intentions). A final aim is to qualitatively assess perceived benefits, concerns, and recommendations related to aU=aU messaging. The proposed training plan in this F31 application will provide the essential knowledge and skills that I need to help reach my goal of becoming an independent scholar. The training I will acquire through this timely and innovative research project, in combination with formal coursework, one-on-one mentorship, focused workshops, academic conferences, manuscript preparation, grant-writing, and other training activities, will target three training objectives: (1) to enhance skills in conducting advanced research methodology, (2) to gain mastery on the topic of health communication, and (3) to gain experience with the dissemination of research and to gain skills in grant writing. I will be mentored by Dr. Sarah K. Calabrese (Sponsor), Co-sponsors: Drs. David Huebner, Jonathon Rendina, and Tamara Taggart, and Scientific advisor: Dr. Ana María del Río González.