Some people should consider taking an antibiotic as a morning-after pill to try to prevent certain sexually transmitted diseases, U.S. health officials recommended Tuesday.

The Centers for Disease Control and Prevention finalized its endorsement of taking doxycycline after unprotected sex as a way to prevent chlamydia, gonorrhea or syphilis infections.

CDC officials called it the first new prevention tool against sexually transmitted infections in decades, and said innovation is badly needed. Rates of syphilis, chlamydia and gonorrhea have been rising for years, most notably in gay and bisexual men, although the latest data suggested chlamydia and gonorrhea cases stopped rising in 2022.

The new guideline is specific to gay and bisexual men and transgender women who had an STD in the previous year and are at high risk of getting infected again. Studies have demonstrated doxycycline works in that group, but there's not sufficient evidence to make the same recommendation for other people, agency officials said.

Officials call the treatment doxy PEP, short for doxycycline postexposure prophylaxis. Doctors can write a prescription for one dose of 200 milligrams of doxycycline to be taken within three days of unprotected sex, the CDC said.

In October, the CDC released a draft version of the guidelines. The proposed language was changed somewhat after a public comment period. Changes include clarifying language that the pills should be taken only once per 24 hours, and that doctors should reassess the regimen with patients every three to six months.