Abstract
INTRODUCTION: We assessed trends in HIV and syphilis prevalence, HIV incidence, related risk factors, and preventive behaviors among men who have sex with men (MSM) in Vietnam from 2015 to 2020. METHODS: Data originated from the HIV Sentinel Surveillance Plus system, which sampled MSM at venues and hotspots in seven of Vietnam's 63 provinces in 2015, 2016, 2018, and 2020 (N = 1100-1445 per year; ∼150-300 per province per year). RESULTS: HIV prevalence estimates increased from 6.6% (95% CI 4.5-9.6) in 2015 to 13.8% (95% CI 10.5-18.2, p = .001 for trend) in 2020 overall, and separately in An Giang, Can Tho, Hai Phong, and Khanh Hoa provinces but not in Ho Chi Minh City, Hanoi, or Kien Giang. Syphilis prevalence increased from 2.7% (95% CI 1.4-5.1) in 2015 to 12.6% (95% CI 8.7-18.0) in 2020 overall (p < .001 for trend), and separately in An Giang, Can Tho, and Hai Phong provinces but not in Ho Chi Minh City or Kien Giang. We calculated time-at-risk from first anal sex to first HIV-positive or last HIV-negative test to estimate HIV incidence. Estimated HIV incidence suggested increasing rates of seroconversion from 1.36 per 100 person-years experienced by participants in 2015 to 2.61 per 100 person-years among participants in 2020 (hazard ratio per year 1.13, 95% CI 1.08-1.18, p < .001). There was a statistically significant increase in HIV testing, STI testing, and receipt of free condoms over the period (p < .05 for trend), and a statistically significant decrease in amphetamine use (p = .043 for trend). CONCLUSIONS: Despite prevention efforts and improvements in some risk indicators, consecutive cross-sectional sampling results provide evidence of increasing incidence of HIV and syphilis among MSM in Vietnam, especially outside the major cities. Aggressive HIV prevention and treatment services can be expanded while conducting deeper investigations into the causes of these increases.