The effect of mandatory regulatory policies on unsafe sexual behaviours among female sex workers: an evaluation study

Social policies shape individual behaviours and population health. Human Immunodeficiency Virus (HIV) prevention governance measures targeting female sex workers (FSWs) remain controversial. Existing evidence mainly relies on qualitative or cross-sectional self-reported data, limiting objective population-level assessments. Using longitudinal data from China’s HIV sentinel surveillance system, we evaluated whether mandatory regulatory measures have influenced unsafe sexual behaviours among FSWs.

We treated the 2015 policy implementation in Baise City, Guangxi, China, as a natural experiment. Using data from eleven counties covered by the National HIV Sentinel Surveillance System (2010–2020), we applied the Cochran–Armitage trend test and interrupted time series analyses to evaluate changes in AIDS knowledge awareness rate (AKAR), condom use rate at last commercial sexual encounter (CUR-LCSE), and active syphilis positivity rate (ASPR). Deviation of ASPR from the expected level was estimated using the event study method, and the policy effect was validated by a robustness test.

Among 19 220 observations, AKAR and CUR-LCSE showed significant upward trends from 2010 to 2020 (both p < 0.01). ASPR remained stable before 2015 (p = 0.53) but declined markedly thereafter (p < 0.01). Event study analyses detected no systematic deviation between observed and expected ASPR; robustness tests indicated that the post-2015 decline was random (t = − 0.956; p = 0.39). Overall, mandatory regulatory policies were not associated with measurable changes in unsafe sexual behaviour.

Mandatory regulatory policies showed no clear evidence of elevated syphilis risk among FSWs. The stable prevalence of active syphilis and consistent behavioural indicators further confirmed that these policies did not inadvertently promote unsafe sexual behaviours, and serological findings indicated a lack of substantial behavioural changes in this population. This highlights an urgent need to clarify how structural and social determinants shape unsafe sexual behaviours to inform the development of more integrated and equitable syphilis prevention strategies.