A Phase 3 interventional study of Experimental: doxycycline and Bexsero® vaccine in Unsafe Sex and Risk-Taking, sponsored by ANRS, Emerging Infectious Diseases. Completed at 9 sites in France. Open to male participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-04-06.
Sponsored by ANRS, Emerging Infectious Diseases · Phase 3, Interventional, and Treatment
The study ANRS 174 Doxyvac is a clinical trial that will use Combined Prevention of Sexually Transmitted Infections (STIs) in Men Who Have Sex with Men and using oral TDF/FTC for HIV Pre-Exposure Prophylaxis (PrEP) and vaccination with Bexsero.
This is a randomized study with a factorial design for the 2 biomedical interventions (interventions 1 and 2).
Subjects will be randomized and assigned to two different interventions:
Participants will be randomized in one of the following arms:
Randomization will be stratified by whether or not the participant enters in the ancillary study "intestinal microbiota".
136 studies on the registry are indexed under Risk-Taking; 18 are open to participants now.
This study's enrollment of 556 is above the median of 255 across 117 interventional studies indexed under Risk-Taking.
Browse Risk-Taking studies →ANRS, Emerging Infectious Diseases is the lead sponsor of 215 studies on the registry; 38 are open to participants now.
Compared within Risk-Taking, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Unsafe Sex. The counts are of registry records indexed under each term, refreshed daily. How we classify →
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
-doxycycline will be taken by participants as PEP (prophylaxy post exposition) and participants will received Meningococcal B vaccine (Bexsero®) at D0 and M2
Drug: Experimental: doxycycline · Biological: Bexsero® vaccine
-doxycycline will be taken by participants as PEP (prophylaxy post exposition)
Drug: Experimental: doxycycline
-Meningococcal B vaccine (Bexsero®) at D0 and M2
Biological: Bexsero® vaccine
-no doxycycline and no Bexsero® vaccine
2 tablets of doxycycline 100 mg (monohydrate form) will be taken orally after each risk sexual intercourse, ideally within 24 hours after sex and no more than 72 hours. PEP should not be taken more than 3 times over a 7 days' period. If a participant has risk sexual intercourse for several consecutive days, PEP should be taken at least 48 hours apart and no more than 3 times 2 tablets over 7 days. A maximum of 3 intakes of 2 tablets will be allowed over a period of 7 days.
1st injection of Bexsero® vaccine at inclusion visit, 2nd injection at week 8.
For intervention 1 (with or without doxycycline PEP) : 1st occurence of chlamydia or syphilis after the enrolment visit (Day 0)
Intervention 1 (with or without doxycycline PEP) is the first episode of chlamydia or syphilis after the enrolment visit (Day 0) (chlamydia and syphilis diagnosed at the enrolment visit will not be included in the primary endpoint). Chlamydia détection will be performed by polymerase chain reaction.Syphilis détection will be performed by antigen.
Time frame: Month 24
For intervention 2 with or without Bexsero® vaccine : 1st occurence of gonorrhea reported one month after the second vaccine injection
Intervention 2 (with or without Bexsero® vaccine) is the first episode of gonorrhea reported one month after the second vaccine injection, so starting at the month 3 visit (gonorrhea episodes diagnosed at the enrolment visit and before the month 3 visit will not be included in the primary endpoint). In these analyses, subject follow-up will be right-censored at the time of the first STI. Gonorrhea détection will be performed by polymerase chain reaction.
Time frame: Month 24
- Occurrence of a first episode of each of the bacterial STIs as well as cumulative incidence of each bacterial STIs
\- Occurrence of a first episode of each of the bacterial STIs as well as cumulative incidence of each bacterial STIs (syphilis, chlamydia; gonorrhoea and Mycoplasma genitalium) during the trial. In that case, the entire follow-up will be considered. Chlamydia détection will be performed by polymerase chain reaction. Syphilis détection will be performed by antigen. Mycoplasma genitalium be performed by polymerase chain reaction. Gonorrhea détection will be performed by polymerase chain reaction.
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Occurrence of a new episode of anal or urinary gonorrhoea.
\- Occurrence of a new episode of anal or urinary gonorrhoea. Gonorrhea détection will be performed by polymerase chain reaction.
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Occurrence of a first symptomatic episode of chlamydia infection or gonorrhea
\- Occurrence of a first symptomatic episode of chlamydia infection or gonorrhea at urinary or anal sites. Chlamydia détection will be performed by polymerase chain reaction. Gonorrhea détection will be performed by polymerase chain reaction.
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Proportion of patient with Methicillin-Resistant Staphylococcus Aureus and/or doxycycline resistant Staphylococcus aureus from throat. Fecal carriage of Extended-Spectrum Beta-Lactamase-producing Enterobacteriaceae Composition of intestinal microbiota
detection from throat swab of carriage of MRSA (methicillin-resistant Staphylococcus aureus) and/or doxycycline resistant Staphylococcus aureus, fecal carriage of ESBL (extended-spectrum beta-lactamase) -producing Enterobacteriaceae, and composition of the intestinal microbiota), all détected by polymerase chain reaction assay
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Incidence of clinical and biological adverse events
Proportion of patients experiencing a clinical or biological adverse events (ANRS scale)
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Proportion of patients taking doxycycline
Adherence will be evaluated by doxycycline pills taken by patients
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Concentration of doxycycline in hair
Adherence will be evaluated by détection of doxycyclin in hair
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Proportion of patients with Antibiotic susceptibilities of all strains of NG (Neisseria gonorrhoeae), CT (chlamydiae trachomatis), MG (mycoplasma genitalium)
identification of Antibiotic susceptibilities of all strains of NG (Neisseria gonorrhoeae), CT (chlamydiae trachomatis), MG (mycoplasma genitalium) to doxycycline, macrolides, fluoroquinolones and third generation cephalosporin will be performed by PCR (polymerase chain reaction assay)
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Rate of cured STIs after treatment with or without PEP.
declaration of illnesses from infection to healing
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Incidence of resistance to antibiotics of Neisseria gonorrhoeae with or without doxycycline.
Proportion of participants with resistance to antibiotics of Neisseria gonorrhoeae will be evaluated by polymerase chain reaction to detect mutations
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Incidence of Serum bactericidal activity against meningococcal and gonococcal antigens over time in participants of Bexsero®'s arm.
Proportion of participants with Serum bactericidal activity against meningococcal and gonococcal antigens
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Incidence of clinical and biological adverse events following Bexsero® vaccine.
Proportion of participants experiencing a clinical and biological adverse events following Bexsero® vaccine (ANRS scale)
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Prevalence and incidence of meningococcal carriage in pharyngeal, anal and urine swabs.
detection of meningococcal carriage in pharyngeal, anal and urine swabs will be performed
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Impact of PEP or Bexsero® vaccine on sexual behaviour
rates of condom use for receptive anal intercourse, number of sexual partners and number of sex acts over time
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
- Incidence of HIV infection with both prophylaxis strategies.
HIV infection will be tested by serology and western blot assay
Time frame: Month 2, Month 3, Month 6, Month 12, Month 18, Month 21, Month 24
This study is completed, as verified in Apr 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Doxycycline
ANRS, Emerging Infectious Diseases →