Undetectable, Unrejectable? The Serodivide in the Era of PrEP and U=U

Abstract

Background: HIV pre-exposure prophylaxis (PrEP) and viral suppression through HIV treatment, known as U=U (‘Undetectable=Untransmittable’), are highly effective at preventing sexual HIV transmission between serodifferent partners. As PrEP and U=U may narrow the so-called ‘serodivide’, we assessed openness to serodifferent partnering nationally among gay and bisexual men (GBM) in Australia for the first time in the biomedical prevention era. Methods: A national online survey of Australian GBM was conducted in June–July 2023. Sexually active participants were asked if they would "refuse" sex or a romantic relationship with a partner living with HIV (PLHIV) (1=strongly disagree to 5=strongly agree). Participants who disagreed were classified as open to serodifferent partnering. Logistic regression identified associated characteristics. Results: Of 2,046 respondents, 1,759 HIV-negative/untested participants with ≥1 sexual partner in the last 6 months were included. Median age was 35.0, 81.2% identified as gay, 70.6% were Australian-born, and 53.3% were current PrEP users. 54.2% perceived U=U as accurate and 52.4% knew ≥1 PLHIV. 75.8% were open to serodifferent sexual partners, and 82.1% of 884 single participants were open to serodifferent romantic partners. Openness to serodifferent sexual partners was associated with perceiving U=U as low (aOR=2.49, 95%CI [1.84, 3.36], p<.001) or zero risk (aOR=6.41, 95%CI [4.39, 9.34], p<.001), current PrEP use (aOR=1.45, 95%CI [1.06, 1.97], p=.019), and knowing ≥1 PLHIV (aOR=2.45, 95%CI [1.87, 3.22], p<.001). Openness to serodifferent romantic partners was associated with perceiving U=U as zero-risk (aOR=3.91, 95%CI [2.18, 7.02], p<.001) and knowing ≥1 PLHIV (aOR=1.67, 95%CI [1.13, 2.46], p=.01). Conclusion: Three-quarters of HIV-negative/untested participants were open to serodifferent partnering (with higher openness to romantic partners). While encouraging, there is room for improvement. Perceiving U=U as zero risk was crucial; promoting understanding of U=U’s message effectiveness is important in bridging the serodivide.