Attitudes, Knowledge, and Worry About HIV in the U=U Era: A Campaign with Before-After Surveys Among HIV-Negative Men Who Have Sex with Men in Sweden.

Despite evidence that undetectable equals untransmittable (U=U), negative attitudes toward people living with HIV persist among men who have sex with men (MSM). We examined HIV-related knowledge, attitudes and relationship willingness among Swedish MSM and evaluated an anti-stigma campaign. Repeated cross-sectional online surveys of MSM aged ≥ 18 years were conducted in Sweden (2020-2021) before and after an anti-stigma campaign. Participants were recruited via LGBTQIA+ media and dating or cruising platforms. Multivariable logistic regression adjusted for sociodemographic and behavioral factors. We analyzed 3100 pooled responses and 1132 post-campaign responses. Knowledge gaps were substantial: 72% had not encountered U=U messaging and only 53% knew that treatment prevents transmission. Nearly half expressed unwillingness to consider relationships with people living with HIV. Negative attitudes decreased with higher knowledge (adjusted odds ratio [aOR] 0.38; 95% confidence interval [CI] 0.28-0.53) and increased with greater worry (aOR 3.66; CI 2.75-4.90). Greater relationship willingness was associated with higher HIV knowledge (aOR 3.79; CI 2.67-5.41). Less negative attitudes and greater relationship willingness were also linked to openness about sexual orientation. Campaign exposure was significantly associated with higher knowledge, less negative attitudes, lower worry, and greater relationship willingness. U=U awareness remains limited and stigma persists. The interrelations between knowledge, worry, and attitudes highlight cognitive and emotional dimensions of stigma. Observed links with campaign exposure suggest potential value of concise, context-specific U=U-centered communication in addressing stigma among MSM.