Effect of a Lottery Intervention on Gender-Based Violence among Female Sex Workers in Dar es Salaam, Tanzania : Results from a Randomized Trial

Financial incentives are a promising approach for HIV prevention. Some studies have shown that financial incentive interventions aimed to promote positive health and social behaviors have mixed or harmful effects on gender-based violence, and little is known about their effects among higher risk groups such as female sex workers. To address this gap, this study investigated the relationship between a lottery-based incentive and gender-based violence among female sex workers in Dar es Salaam, Tanzania. Data were analyzed from the RESPECT II trial, which enrolled 2,206 female sex workers in Dar es Salaam, Tanzania, to evaluate the effect of a lottery-based incentive on HIV and sexually transmitted infections. Participants were randomized in a one-to-one ratio to: (1) the basic test group (control), which provided baseline testing and counseling for HIV and sexually transmitted infections and bi-weekly text messages on safe sex practices; or (2) the lottery group, which included the basic test group intervention plus entry into a weekly random lottery for an award of 100,000 Tanzanian shillings conditional on negative tests for sexually transmitted infections (syphilis and trichomonas vaginalis). An intent-to-treat analysis was conducted to estimate differences in physical and sexual gender-based violence (overall), and intimate partner violence and non-partner violence between treatment arms at endline, with estimates expressed as unadjusted prevalence differences with 95 percent confidence intervals. Adjusted estimates controlled for baseline reports of violence. Multiple imputation and inverse-probability of treatment weighting were used to account for missing data. Causal, population-level impacts were estimated using g-computation. Gender-based violence, intimate partner violence, and non-partner violence declined in both treatment arms over the study period among the sample of 1,117 female sex workers retained at endline. The lottery group had a lower prevalence of gender-based violence overall, intimate partner violence, and non-partner violence compared to control at endline; however, the differences were not statistically significant. The results indicate that the lottery intervention had no effect on violence outcomes among endline participants in the RESPECT II trial. These results suggest that this economic approach does not pose additional risks of violence in the context of sex work; however, they must be interpreted with caution due to high attrition in the study sample. Additional research is warranted to examine how this incentive mechanism impacts violence for female sex workers.