Correlates of unprotected sex by client type among female sex workers that inject drugs in Tijuana and Ciudad Juarez, Mexico

Aims: Risk environment factors may influence unprotected sex between female sex workers who are also injection drug users (FSW-IDUs) and their regular and non-regular clients differently. Our objective is to identify correlates of unprotected vaginal sex in the context of client type. Methods: A cross-sectional survey of 583 FSW-IDUs in Tijuana and Ciudad Juarez, Mexico, was analyzed using negative binomial regression to determine physical, social, economic, and policy risk-environment factors that affect the frequency of unprotected sex with regular and non-regular clients. Results: Median number of unprotected vaginal sex acts in the past month among FSW-IDUs and their regular and non-regular clients was 11 (IQR 3-30) and 13 (IQR 5-30), respectively. Correlates differed by site and client type and were most closely associated with the risk environment. In Tijuana, social factors (e.g., injecting drugs with clients) were independently associated with more unprotected sex. Factors independently associated with less unprotected sex across client type and site included social and economic risk environment factors (e.g., receiving more money for unprotected sex). In the policy risk environment, always having free access to condoms was independently associated with less unprotected sex among non-regular clients in Tijuana (Risk rate ratio = 0.64; 95% confidence interval 0.43-0.97). Conclusions: Primarily physical, social, and economic risk-environment factors were associated with unprotected vaginal sex between FSW-IDUs and both client types, suggesting potential avenues for intervention.