Photo Credit: Viktoriia Hnatiuk

The following is a summary of “Doxycycline prophylaxis and meningococcal group B vaccine to prevent bacterial sexually transmitted infections in France (ANRS 174 DOXYVAC): a multicentre, open-label, randomised trial with a 2 × 2 factorial design,” published in the October 2024 issue of Infectious Diseases by Molina et al. 

Men who have sex with men (MSM) encounter high sexually transmitted infections (STIs) rates, requiring new interventions.    

 Researchers conducted a retrospective study to assess the effectiveness of post-exposure prophylaxis (PEP) with doxycycline and the meningococcal group B vaccine (4CMenB) in MSM, reducing STI incidence.  

 They designed the study in 10 Paris hospitals where eligible participants were HIV-negative MSM aged 18 or older with recent bacterial STIs who were randomly assigned (2:1) to doxycycline PEP (2 pills of 100 mg each orally within 72 h after condomless sex, with no more than 3 doses of 200 mg per week) or no PEP, and (1:1) to 4CMenB (GlaxoSmithKline, Paris, France; 2 intramuscular injections at enrolment and 2 months) vaccine or no vaccine. Follow-up was for at least 12 months, with 3 months of regular visits. The coprimary outcomes were the risk of a 1st episode of chlamydia or syphilis (or both) after baseline for doxycycline and the risk of a 1st episode of gonorrhea starting at month 3 for the vaccine and analyzed these outcomes in the modified intention-to-treat population.   

 The results showed that 545 male participants were included in the modified intention-to-treat analysis for doxycycline PEP and no PEP groups, and 544 for the 4CMenB vaccine and no vaccine groups. The median follow-up was 14 months (IQR 9–18), and the median age of 545 participants was 40 years (34–48) with no interaction between the 2 interventions (P≥0·1). The incidence of a 1st episode of chlamydia or syphilis (or both) was 8·8 per 100 person-years (35 events in 362 participants) in the doxycycline PEP group and 53·2 per 100 person-years (80 events in 183 participants) in the no PEP group (adjusted hazard ratio [aHR] 0·17 [95% CI 0·12–0·26]; P<0·0001) while incidence of  1st episode of gonorrhea, starting from month 3, was 58·3 per 100 person-years (103 events in 274 participants) in the 4CmenB vaccine group and 77·1 per 100 person-years (122 events in 270 participants) in the no vaccine group (aHR 0·78 [95% CI 0·60–1·01]; P=0·061) with no deaths reported with1 drug-related adverse severe event (fixed-drug eruption) occurred in the doxycycline PEP group along with 6 (2%) participants in the doxycycline group discontinued doxycycline PEP because of gastrointestinal adverse events.   

Investigators concluded that doxycycline PEP effectively lessened the incidence in MSM of chlamydia and syphilis, but the 4CMenB vaccine was not efficient for gonorrhea.    

 Source: thelancet.com/journals/laninf/article/PIIS1473-3099(24)00236-6/abstract