Meta-analysis finds doxycycline prophylaxis reduces STI risk in MSM and transgender women

BACKGROUND: Recent systematic reviews have demonstrated the efficacy of doxycycline prophylaxis in preventing bacterial sexually transmitted infections (STIs) in randomised controlled trials (RCTs). In this review, we updated evidence from RCTs and non-RCTs and compared the effectiveness of doxycycline as pre- (doxy PrEP) and post-prophylaxis (doxy PEP) across different groups. METHODS: We searched PubMed, Web of Science, Embase, Cochrane Library, and two conference abstract archives for publications from January 2010 to April 2025. Eligible RCT and non-RCT studies on doxy PrEP and doxy PEP to prevent STIs were included in the analysis. Pooled risk ratios were calculated using fixed-effects and random-effects models. This study was registered with PROSPERO (CRD42024568934). RESULTS: Fourteen eligible studies (4 doxy PrEP, 10 doxy PEP) were included for analysis. Participants were primarily men who have sex with men (MSM) and transgender women (TGW). Doxycycline (either PrEP or PEP) reduced the risk of acquiring any STIs by 60% (risk ratio (RR), 0.40; 95% CI, 0.30-0.52) in RCT and non-RCT trials. Doxycycline was associated with fewer incidences of chlamydia (RR, 0.18; 95% CI, 0.11-0.28), gonorrhoea (RR, 0.61; 95% CI: 0.44-0.86), and syphilis (RR, 0.20; 95% CI; 0.12-0.33). Meta-analysis of seven RCTs showed 76% decrease on chlamydia (RR: 0.24; 95% CI: 0.13-0.45), 33% decrease on gonorrhoea (RR, 0.67; 95% CI; 0.45-0.98), and 78% decrease on syphilis (RR, 0.22; 95% CI; 0.14-0.36). HIV-positive and HIV-negative people benefited from using doxy PrEP and PEP regimens prevented bacterial STIs. CONCLUSIONS: RCT and non-RCT data demonstrated the effectiveness of doxy PrEP and doxy PEP in reducing STIs among MSM/TGW. Integrating doxy PrEP or doxy PEP as a biomedical tool into STI prevention strategies should be considered.