Messaging about HIV Transmission Risk When Viral Load Is Undetectable: Reactions and Perceived Accuracy among US Sexual Minority Men

Background: Scientific evidence indicates that HIV viral suppression to an undetectable level eliminates sexual transmission risk ("Undetectable=Untransmittable” or “U=U”). However, U=U messaging has been met with skepticism among sexual minority men (SMM) and others. In this survey-based experiment, we manipulated messaging about HIV risk and examined reactions and perceived message accuracy among US SMM. Methods: SMM living with HIV ( n =106) and HIV-negative/status-unknown SMM ( n =351) participated in an online survey (2019-2020). Participants were randomly assigned to one of three messaging conditions, which varied by level of HIV sexual transmission risk associated with an undetectable viral load (No Risk U=U/Low Risk/Control). Participants reported reactions, message accuracy, and reasons for perceiving inaccuracy. We coded open-response data (reactions and reasons) into conceptual categories (e.g., “Enthusiasm”). We compared reactions, accuracy ratings, and reasons by condition and serostatus. Results: In the No Risk Condition, common reactions were Enthusiasm (40.0%), Skepticism/Disagreement (20.0%), and Agreement (19.4%), reactions common to comparison conditions. A higher percentage of HIV-negative/status-unknown participants (24.1%) expressed Skepticism/Disagreement in the No Risk Condition compared with other conditions (3.2%-9.7%). Participants living with HIV were more likely than HIV-negative/status-unknown participants to perceive all messages as accurate. In the No Risk Condition, common reasons for perceiving inaccuracy were Risk Misstated (46.1%), Oversimplified/Caveats Needed (17.1%), and Personal Unfamiliarity/Uncertainty (14.5%), reasons common to comparison conditions. Across conditions, 10.3% of participants attributed message inaccuracy to misdefinition of undetectable. Conclusion: Most SMM reacted favorably to U=U messaging. However, many—especially HIV-negative/status-unknown SMM—expressed skepticism. Interventions are needed to enhance U=U understanding and acceptance.