Preventing sexually transmitted infections (STIs) like chlamydia and gonorrhea with an antibiotic and a vaccine is possible. A French study conducted among 500 men who have sex with men and are at risk of STIs shows that the antibiotic doxycycline and a vaccine against meningococcal B are effective in reducing the incidence of these diseases. A “major step forward”, according to the Dr Réjean Thomas, president and founder of the L’Actuel clinic.
The results of the French DoxyVAC study, conducted by the National Agency for Research on AIDS and Viral Hepatitis (ANRS), were presented Monday in Seattle at the Conference on Retroviruses and Opportunistic Infections 2023.
According to its authors, doxycycline — when taken within 72 hours of unprotected sex — reduces the risk of chlamydia and syphilis by just over 80%, and the risk of gonococcal infection by almost 50%. in men who have sex with men taking pre-exposure prophylaxis to prevent HIV.
The meningococcal B vaccine [Bexsero] reduces the risk of gonococcal infection by almost 50%”, indicates in an interview with the Duty the coordinating investigator of the study, Dr.r Jean-Michel Molina, who heads the infectious and tropical diseases department at the Saint-Louis AP-HP hospital in Paris. “This is the first randomized clinical trial to confirm the benefit of the meningococcal B vaccine against gonococci. »
The effect of doxycycline on the prevention of STIs was already known. A smaller study led by Dr.r Molina and published in 2017 had shown its effectiveness. American researchers had also presented results along the same lines at the International AIDS Conference in Montreal in 2022.
A “major step forward”
Faced with its conclusive data and the absence of serious adverse effects, the ANRS decided to offer doxycycline and the meningococcal B vaccine last October to all participants in its research, including the control group, thus putting end the study in its original form.
For the Dr Thomas, the results of DoxyVAC are “a major step forward in the fight against sexually transmitted infections”. “STIs can have serious consequences – especially gonorrhea and chlamydia, which are major causes of infertility and chronic pain,” he points out. Not to mention that the treatment and follow-up of these patients entail costs for the Quebec health system.
STIs are on the rise in Quebec. The National Institute of Public Health of Quebec (INSPQ) describes as an “epidemic” the increase in cases of chlamydia and gonorrhea in newest sound Portrait of sexually transmitted and blood-borne infections (STBBIs) in Quebec, dating from 2019 and published last spring. He considers “concerning” the “significant” increase in syphilis infections in recent years.
The Dr Thomas believes that doxycycline and the meningococcal B vaccine are promising strategies to prevent STIs. He has also started to offer the antibiotic and the vaccine to his “most at risk” patients. The latter are on pre-exposure prophylaxis (as in the study), because they have very little or no use of condoms during sexual relations.
“The problem right now is that each dose of Bexsero vaccine costs $143,” says Dr.r Thomas. You have to take two. The vaccine is not covered by the Régie de l’assurance maladie du Québec (RAMQ) for this indication. The results of the study having just been published, Public Health has obviously made no recommendation on this subject.
“If the vaccine could be provided by Public Health in the context of a pilot project, that would be interesting,” says Dr.r Thomas. These are things we would like to discuss with them. According to him, access to the antibiotic – which is also not covered by the RAMQ in this preventive context – does not pose a problem: the generic drug is “inexpensive”.
In Quebec, some 4,000 people use pre-exposure prophylaxis, according to the RAMQ. These could eventually benefit from doxycycline and the meningococcal B vaccine, thinks the Dr Thomas.
Antibiotic resistance?
The frequent use of antibiotics to prevent STIs nevertheless raises questions. “It is true that giving antibiotics repeatedly can be a problem, because we can have an impact on the emergence of resistance in bacteria to antibiotics”, recognizes the Dr Molina, also a professor at Paris Cité University.
According to him, it may be better to offer doxycycline to a targeted group: “people who really need it” and “people who have a lot of sexually transmitted infections” (and who therefore are already taking antibiotics to treat these diseases). “And maybe not for a long time,” he says.
In short, caution remains in order for the moment. According to the D.r Molina, more data and verification are needed to ensure that this means of prevention does not have a “deleterious effect” on antibiotic resistance in the population. He and his colleagues will continue to follow the 500 participants in the initial study until September 2023.