An effective antibiotic and vaccine to prevent sexually transmitted infections

According to a French study, taking Doxycycline after an unprotected sexual intercourse and vaccination against meningococcal B strongly reduce the risk of infection in chlamydia, syphilis or gonorrhea.

by Florence Rosier

Prevention was in the spotlight, during the 30 e edition of the conference on retroviruses and opportunistic infections, which was held from February 19 to 22 in Seattle (States- United). Particularly prevention against sexually transmitted infections (IST). Two effective strategies were presented there. A French study thus confirmed the interest, against bacterial STI, of a preventive dose of a well -known antibiotic, doxycycline, taken one to three days after a sexual intercourse without condom. This antibiotic is conventionally recommended in the treatment of urethra infections, cervix, uterine tubes or anus. It is also indicated in the treatment of syphilis, Lyme disease, certain skin diseases (rosacea, acne, etc.), dental infections and diarrhea of ​​bacterial origin, but also in prevention of malaria.

The concept of prevention postxposition by DoxycyCine emerged at the end of 2017, during the Ipergay test, led by the National Agency for Research on AIDS and Viral Hepatitis (ANRS). Used in the twenty-four to seventy-two hours after intercourse, this antibiotic reduced by around 70 % the risk of infection in chlamydia and syphilis.

At the same time, various epidemiological studies have reported, in recent years, that people vaccinated against meningococcal B (with the GSK Bexserto vaccine) could see the risk of gonococcal infection decrease by around 30 %. “There are common antigens between meningococcus B and gonococcus,” explains Jean-Michel Molina, head of the infectious and tropical disease service at Saint-Louis Hospital and Lariboisière Hospital (Paris-Cité University), D ‘Where possible cross protection conferred by the antimeningococcal vaccine against this ist.

No severe adverse effect

The Doxyvac study, coordinated by Jean-Michel Molina, was promoted and funded by the ANRS. Between January 2021 and July 2022, the researchers recruited 502 men’s volunteers (whose median age is 39 years) with sex with men (with a median of ten sexual partners in the last three months) and living in the region Parisian. All were under PREP (preventive HIV treatment) and had a history of STI in the previous year. They were distributed by drawing in four groups, according to the rules of “randomized” trials. The first benefited from a postxposition prevention by doxycycline (in the twenty-four to seventy hours after an unprotected sex), the second of a vaccination against meningococcus B, the third of the combination of these two interventions and the last had no intervention.

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