A French study demonstrates the effectiveness of a strategy for preventing several sexually transmitted infections (STIs) by combining a vaccine and a common antibiotic.
The announcement did not go unnoticed at the conference specializing in HIV/AIDS research (better known as the Cut), which brought together in Seattle, from February 17 to 22, thousands of researchers, doctors and members of NGOs.
This study funded by the ARNS in partnership with the Roche laboratory, demonstrates the effectiveness of a strategy for the prevention of several sexually transmitted infections (STIs) by combining a vaccine and a common antibiotic.
Impressive numbers
The numbers are impressive. The reduction in the risk of infection by STIs chlamydia and syphilis is 85% between those who received the antibiotic doxycycline, taken within 72 hours of sexual intercourse, and those who had not received it.
In parallel, the study, coordinated by Pr Jean-Michel Molina (Saint-Louis Hospital) and conducted in the Paris region, showed the effectiveness of the Bexsero vaccine in preventing infection by gonococcus. After three months, the incidence of a first episode of gonococcal infection in the group vaccinated with Bexsero and the unvaccinated group was 9.8 and 19.7 per 100 person-years. This means a reduction in incidence of 51%.
Good news, considering that in recent years there has been a significant increase in these three STIs, especially among men who have sex with men (MSM).
Between January 2021 and July 2022, 502 MSM volunteers were randomly divided into four groups: one receiving post-exposure prophylaxis with doxycycline to be taken within 72 hours after unprotected sex with a condom, the the other a Bexsero vaccination, the third the combination of these two interventions and the last none of the two interventions.
The volunteers had a median age of 39 years, about ten sexual partners in the last three months and benefited from an average follow-up of nine months. They were monitored and tested every three months for symptoms for gonococcal and chlamydial infections and for syphilis.
Via press release Professor Molina says: “The use of doxycycline for post-exposure prophylaxis has been shown to be effective in reducing the incidence of both chlamydial infections and syphilis. This antibiotic also had a significant impact, as did the meningococcal B vaccine, on the incidence of gonococcal infections. This is the first time that a vaccine has shown an effect on a bacterial sexually transmitted infection”.
Monitoring of participants will continue until the end of 2023 to ensure the medium-term effectiveness of these prevention strategies, which have now been offered to all participants.
Effectiveness of mpox vaccine
Data from these same participants in the DOXYVAC study were analyzed to measure the preventive impact of the MVA-BN vaccine against mpox shortly after the outbreak of what was then called monkeypox. According to the ANRS, “the research team found that the single vaccination against the mpox virus in 2022 was associated with a reduced risk of developing the disease with an effectiveness of 99%”.
This strategy is added to other prevention tools to reduce the risks (repeated screening for HIV and STIs, vaccination against hepatitis A and B, distribution of condoms and gels).