Modelling the impact of underage and coerced entry into sex work on HIV transmission in Tijuana, Mexico.

BACKGROUND

Some female sex workers (FSW) are initiated into sex work underage (<18 years) and/or through coercion, potentially increasing vulnerability. We estimated the contribution of these factors to HIV transmission in Tijuana, Mexico.

METHODS

Using data from three bio-behavioural studies among adult FSWs in Tijuana (2003-2015), regression analysis assessed associations between underage or coerced entry into sex work and increased sexual or injecting risk behaviours. A dynamic HIV transmission model projected the proportion of new HIV infections prevented among FSWs over 2025-2034 from removing any additional risk behaviours associated with underage or coerced entry into sex work.

RESULTS

Across studies (881 FSW), 10.1-39.0% of FSW reported initiating sex work underage, which was associated with client volume (adjusted rate ratio: 1.33; 95%CI:1.15-1.54), recent injecting drug use (IDU last 6 months) (adjusted odds ratio [aOR]: 1.74; 95%CI:1.08-2.79) and decreased odds of always using condoms (aOR: 0.75; 95%CI:0.53-1.06). Additionally, 19.0-20.7% reported coerced entry into sex work, which was marginally associated with recent IDU (aOR: 1.50; 95%CI:0.97-2.31).Removing the additional risks associated with underage or coerced entry into sex work from 2025 could prevent 33.0% (95%CrI:23.8-40.8%) of HIV infections amongst FSWs that started underage, 18.5% (95%CrI:11.3-28.3%) among FSW that were coerced, and 10.3% (95%CrI:6.8-14.5%) among all FSWs. If underage and coerced entry into sex work could also be stopped, then 22.3% (95%CrI:18.4-26.9) of HIV infections could be prevented among all FSWs.

CONCLUSIONS

Underage and coerced entry into sex work could be important drivers of HIV transmission among FSWs in Tijuana.