RKI and ECDC propose harmonized methods for doxycycline STI prevention studies

Interest in doxycycline prophylaxis to prevent sexually transmitted infections is increasing, alongside concerns about antimicrobial resistance, effects on the human microbiome, long-term safety and equitable access. Existing evidence varies across populations, endpoints and settings. Most efficacy data come from randomized trials involving men who have sex with men and transgender women living with HIV or taking HIV pre-exposure prophylaxis; real-world evidence, particularly for syphilis, often comes from heterogeneous observational or implementation settings.

To improve comparability, the Robert Koch Institute (RKI), in collaboration with the European Centre for Disease Prevention and Control (ECDC), has prepared a practical guide for designing and conducting studies. It proposes standardized variables, operational definitions and minimum datasets intended for use across different study designs and implementation contexts. The guide aims to support comparisons between countries and programmes, pooling of data on uncommon outcomes, and assessment of benefits, risks and unintended population-level effects, including antimicrobial resistance. It is a study-harmonization resource, not a report of new efficacy or safety findings.