For years, bacterial vaginosis has been treated as a simple imbalance in the vaginal microbiome, but a groundbreaking study now confirms it is actually a sexually transmitted infection.
Researchers found that treating both sexual partners drastically reduces recurrence rates, challenging long-standing medical guidelines.
BV Identified as an STI, Changing the Game
A major study has confirmed that bacterial vaginosis (BV), a condition affecting nearly one in three women worldwide and linked to infertility, premature birth, and newborn deaths, is actually a sexually transmitted infection (STI). This discovery could transform the way BV is treated.
Researchers from Monash University and Alfred Health at the Melbourne Sexual Health Centre published their findings today (March 5) in the New England Journal of Medicine, offering a potential breakthrough in reducing BV’s high recurrence rates.
Currently, BV is treated as an imbalance in the vaginal microbiome, but this approach has major drawbacks. According to study authors Professor Catriona Bradshaw and Dr. Lenka Vodstrcil, more than half of women experience a recurrence within three months of completing the standard week-long oral antibiotic treatment.
Groundbreaking Trial Proves Partner Treatment Works
The research team conducted a clinical trial involving 164 monogamous couples where the woman had BV. They found that treating both sexual partners at the same time led to significantly higher cure rates compared to the conventional approach of treating only the woman.
The results were so compelling that the trial was stopped early when data showed that partner treatment reduced BV recurrence by half.
A Simple, Short Treatment With Big Impact
“This successful intervention is relatively cheap and short and has the potential for the first time to not only improve BV cure for women, but opens up exciting new opportunities for BV prevention, and prevention of the serious complications associated with BV,” Professor Bradshaw said.
In the multicentre randomized trial, all women received first-line recommended antibiotics. Male partners were randomly assigned to either partner-treatment, where they received both an oral antibiotic and a topical antibiotic cream for one week, or to a control group. The control group for this trial received female antibiotic treatment only and no partner-treatment, which is the global recommended practice. Couples only took antibiotics for one week but were then followed up for 12 weeks to establish how effective this intervention was in curing BV over 3 months.
BV’s Connection to Other STIs
Dr. Vodstrcil said having BV was already known to increase the risk of contracting other STIs. “We’ve suspected for a long time that it’s a sexually transmitted infection (STI), because it has a similar incubation period (after sex) to most STIs and is associated with the same risk factors as STIs like chlamydia, such as change in sexual partner and not using condoms.”
Professor Bradshaw said while studies have shown that men may harbor bacterial species associated with bacterial vaginosis on the penile skin and inside the penis, previous trials that included male partners did not show improved cure rates in their female partners.
Why Earlier Studies Got It Wrong
“This was interpreted as evidence against sexual transmission,” Professor Bradshaw said. “However, these studies had design limitations, and none used a combination of oral and topical antibiotics to adequately clear BV bacteria in men, especially from the penile-skin site.
“Our trial has shown that reinfection from partners is causing a lot of the BV recurrence women experience, and provides evidence that BV is in fact an STI.”
Genomic Science May Solve the BV Mystery
“Part of the difficulty in establishing whether BV is sexually transmitted has been that we still don’t know precisely which bacteria are the cause, but advances in genomic sequencing are helping us close in on that mystery,” Professor Bradshaw said.
The results have already led to the Melbourne Sexual Health Centre changing its clinical practice to treat couples. A new website for health professionals and consumers provides all the information needed to prescribe and access partner treatment.
“This information has been co-designed with consumers and participants in the trial and health professionals to make it accessible to all,” Professor Bradshaw said. “Changes in national and international treatment guidelines always take time, so we felt an obligation to provide accurate online and downloadable information at the time that the results of the trial are published.”
Reference: “Male-Partner Treatment to Prevent Recurrence of Bacterial Vaginosis” by Lenka A. Vodstrcil, Erica L. Plummer, Christopher K. Fairley, Jane S. Hocking, Matthew G. Law, Kathy Petoumenos, Deborah Bateson, Gerald L. Murray, Basil Donovan, Eric P. F. Chow, Marcus Y. Chen, John Kaldor and Catriona S. Bradshaw, 5 March 2025, New England Journal of Medicine.
DOI: 10.1056/NEJMoa2405404
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