Background: Sexual transmission among men who have sex with men (MSM) has become the major HIV transmission route. However, limited research has been conducted to investigate the association between transactional sex (TS) and HIV incidence in China. Objective: This study aims to investigate HIV incidence and distinguish sociodemographic and sexual behavioral risk factors associated with HIV incidence among MSM who engage in TS (MSM-TS) in China. Methods: We conducted a prospective cohort study using a WeChat-based platform to evaluate HIV incidence among Chinese MSM, including MSM-TS in Ningbo, recruited from July 2019 until June 2022. At each visit, participants completed a questionnaire and scheduled an appointment for HIV counseling and testing on the WeChat-based platform before undergoing offline HIV tests. HIV incidence density was calculated as the number of HIV seroconversions divided by person-years (PYs) of follow-up, and univariate and multivariate Cox proportional hazards regression was conducted to identify factors associated with HIV incidence. Results: A total of 932 participants contributed 630.9 PYs of follow-up, and 25 HIV seroconversions were observed during the study period, resulting in an estimated HIV incidence of 4.0 (95% CI 2.7-5.8) per 100 PYs. The HIV incidence among MSM-TS was 18.4 (95% CI 8.7-34.7) per 100 PYs, which was significantly higher than the incidence of 3.2 (95% CI 2.1-5.0) per 100 PYs among MSM who do not engage in TS. After adjusting for sociodemographic characteristics, factors associated with HIV acquisition were MSM-TS (adjusted hazard ratio [aHR] 3.93, 95% CI 1.29-11.93), having unprotected sex with men (aHR 10.35, 95% CI 2.25-47.69), and having multiple male sex partners (aHR 3.43, 95% CI 1.22-9.64) in the past 6 months. Conclusions: This study found a high incidence of HIV among MSM-TS in Ningbo, China. The risk factors associated with HIV incidence include TS, having unprotected sex with men, and having multiple male sex partners. These findings emphasize the need for developing targeted interventions and providing comprehensive medical care, HIV testing, and preexposure prophylaxis for MSM, particularly those who engage in TS.

BACKGROUND Sexual transmission among men who have sex with men(MSM) has become the major HIV transmission route. However, little is known about the association between transactional sex(TS) and HIV incidence in China. OBJECTIVE This study aimed to investigate HIV incidence and distinguish sociodemographic and sexual behavioral risk factors associated with HIV incidence among MSM who engage in TS (MSM-TS) in China. METHODS We conducted a prospective cohort study using a WeChat-based platform to assess the HIV incidence among Chinese MSM, including MSM-TS in Ningbo, recruited from July 2019 until June 2022. At each visit, participants completed an online questionnaire and made an appointment for HIV counseling and testing on the Wechat-based platform before they had HIV tests offline. HIV incidence density was calculated as the number of HIV seroconversions divided by person-years(PYs) over the observed time, and univariate and multivariate Cox proportional hazards regression was conducted to identify factors associated with HIV incidence. RESULTS 932 participants contributed 630.9 PYs of follow-up, and 25 HIV seroconversions occurred during the follow-up period, yielding an estimated HIV incidence of 4.0/100 PYs(95%CI:2.7~5.8). HIV incidence among MSM-TS was 18.4/100 PYs(95%CI:8.7~34.7), which was significantly higher than that of 3.2/100 PYs(95%CI:2.1~5.0) among MSM who do not engage in TS (MSM-NTS). After adjusting for sociodemographic characteristics, factors associated with HIV acquisition were being MSM-TS (aHR=3.93,95% CI:1.29~11.93), having unprotected sex with men(aHR=10.35, 95%CI:2.25~47.69) and multiple male sex partners (aHR=3.43, 95%CI:1.22~9.64) in the past six months. CONCLUSIONS This study found that the incidence of HIV among MSM-TS in Ningbo was high. The risk factors associated with HIV incidence include TS, having unprotected sex with men and multiple male sex partners, emphasizing the need for developing new interventions and providing medical care, HIV testing, and pre-exposure prophylaxis for MSM, particularly MSM-TS.