The CDC now wants transgender women (TGW) and men who have sex with men (MSM) who are at risk of STIs to take Doxycycline within 72 hours of sex to prevent the spread of chlamydia, gonorrhea, and syphilis. They believe the benefits outweigh the risk of developing new antibiotic resistant strains.
https://www.regulations.gov/document/CDC-2023-0080-0001Based on the clinical trials, systematic reviews, and studies of populations who would likely benefit most from an intervention to reduce bacterial STIs, the following considerations are recommended: doxycycline 200mg taken once orally within 72 hours of oral, vaginal or anal sex should be considered for gay, bisexual, and other MSM, and for TGW, with a history of at least one bacterial STI (i.e., gonorrhea, chlamydia or syphilis) in the last 12 months and who are at ongoing risk for acquisition of bacterial STIs. Although not directly assessed in the trials included in these guidelines, doxycycline PEP could be considered for MSM and TGW who have not been diagnosed with an STI in the prior year but will be participating in sexual activities that are known to increase likelihood of exposure to STIs, e.g., during weekend events, cruises, and festivals.