CDC released a web page in early December outlining guidelines, considerations, and tools (e.g., a palm card) for prescribing Doxy PEP for prevention of STIs. The webpage sums it up: "Doxy PEP has proven to reduce the risk of getting some bacterial STIs for gay, bisexual, and other men who have sex with men and transgender women at increased risk for STIs (specifically, syphilis, chlamydia, and in some studies, gonorrhea)."
Access Doxy PEP for Bacterial STI Prevention and the HRSA HIV/AIDS Bureau Dear Colleague letter to the RWHAP on DoxyPEP.