Objective The HIV trend among female sex workers (FSWs) is understudied. We assessed the prevalence and trend of HIV and five other STIs among FSWs in Iran.

Methods We recruited FSWs (1337 in 2015, 1005 in 2010) from 21 sites in 13 cities in two cross-sectional biobehavioural surveys. Eligible FSWs were women aged ≥18 years who reported selling sex to more than one male client in the past 12 months. Consenting FSWs were interviewed using a behavioural questionnaire and tested for HIV and five other STIs. We considered study sites as clusters in the analysis and two-sided Fisher’s exact test to compare the HIV prevalence between the two survey rounds.

Results HIV prevalence was 2.1% in 2015 (vs 4.0% in 2010, p=0.007). Lifetime drug injection was reported by 6.1% of participants in 2015 (vs 14.6% in 2010, p=0.003). In 2015, among FSWs with history of lifetime drug injection, HIV prevalence was 8.6% (vs 9.8% in 2010, p=0.425). The prevalence of other STIs in 2015 was 0.4% (95% CI 0.2 to 1.0) for syphilis, 1.3% (95% CI 0.8 to 2.1) for gonorrhoea, 6.0% (95% CI 4.8 to 7.4) for chlamydia, 11.9% (95% CI 8.5 to 16.5) for trichomoniasis and 41.8% (95% CI 39.2 to 44.5) for human papillomavirus.

Conclusions HIV prevalence among FSWs in Iran decreased, but remains considerably high. The decrease in HIV prevalence compared with 2010 might be explained by a decrease in drug injection. Other STIs are also high in this population. Harm reduction programmes need to be continued and scaled up among this underserved population in Iran.