Expanded antiretroviral treatment, sexual networks, and condom use: Treatment as prevention unlikely to succeed without partner reduction among men who have sex with men in China

Background: To project the impact of partner reduction on preventing new HIV infections among men who have sex with men (MSM) under varying conditions of enhanced HIV testing and treatment (T&T) and condom use in Beijing, China. Methods and findings: A complex network model was fitted to predict the number of new HIV infections averted from 2014 to 2023 under four scenarios of sexual behavior risk reduction (S)—S1: Male sexual partners decrease (reduced by a random value m from 1–50) while condom use increases (risk constant p is a random value between 0.2 and 1]); S2: Both sexual partners and condom use decrease (m 1, 50; p 1, 1.8); S3: Sexual partners reduce (m 1, 10) while condom use increases or decreases (p 0.2, 1.8); S4: Only MSM with ≥100 male sexual partners reduce their partners (m 1, 50) while condom use increases (p 0.2, 1). Conclusion: Partner reduction is a vital factor within HIV combination interventions to reduce HIV incidence among Beijing MSM, with substantial additional benefits derived from condom use. T&T without substantial partner reduction and increased condom use is less promising unless its implementation were extremely (and improbably) efficient.