New Study Suggests Bacterial Vaginosis May be Sexually Transmitted
New research shows that treating both men and women with topical and oral antibiotics lowers the odds of bacterial vaginosis recurrence by more than half.
The addition of treatment for male partners of women with bacterial vaginosis (BV) significantly reduced the recurrence of the infection in a randomized controlled trial compared with treating only the women, researchers reported.1
The study of monogamous couples published in The New England Journal of Medicine was stopped early because BV recurrence was cut in half among women who received first-line recommended antimicrobial agents and whose male partners also received topical and oral antimicrobial treatment, compared with the control group, in which only the women received first-line antimicrobial treatment.1
BV is a disruption of the vaginal microbiome and affects one-third of reproductive-aged women, and recurrence is common, investigators noted.1 Side effects include adverse birth outcomes, increased risk of sexually transmitted infections (STIs), and pelvic inflammatory disease.2
Study authors said the findings suggest that reinfection from male sexual partners contributes to BV recurrence and supports the idea that it should be considered an STI.1
"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," co-lead investigator Catriona Bradshaw, PhD, of Monash University and the Melbourne Sexual Health Centre, said in a university press release.3
Bradshaw and colleagues conducted the open-label trial from April 2019 through November 2023 involving couples in which the woman had BV and was in a monogamous relationship with a male partner. The study aimed to determine whether treating male partners with antimicrobial therapy would decrease the recurrence of BV in women.1
Participants were divided into two groups: one in which only the woman received standard first-line BV treatment, and another in which both the woman and her male partner received treatment. The male partners in the treatment group were prescribed oral metronidazole (400 mg) and topical clindamycin cream (2%) applied to the penile skin, both administered twice daily for 7 days. The primary endpoint was BV recurrence within 12 weeks. Of the 357 couples assessed for eligibility, 164 underwent randomization, with 81 assigned to the partner-treatment group and 83 to the control group.1
The study was halted early by the data and safety monitoring board after 150 couples completed the 12-week follow-up, as results demonstrated a clear benefit of treating male partners.1
Recurrence of BV occurred in 24 of 69 women (35%) in the partner-treatment group (recurrence rate, 1.6 per person-year; 95% CI, 1.1 to 2.4) compared with 43 of 68 women (63%) in the control group (recurrence rate, 4.2 per person-year; 95% CI, 3.2 to 5.7). This corresponded to an absolute risk difference of –2.6 recurrences per person-year (95% CI, –4.0 to –1.2) and a 63% lower risk of recurrence (HR, 0.37; 95% CI, 0.22-0.61) among women in the partner-treatment group.1
Men in the partner-treatment group experienced some adverse effects, including nausea, headache, and metallic taste, but these were not severe, according to the results.1
“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,” Bradshaw added in the press release.3 “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.”
In an accompanying editorial, Christina A. Muzny, MD, MSPH, professor of medicine at the University of Alabama-Birmingham, and Jack D. Sobel, MD, dean of the Wayne State University School of Medicine, said the results represent a "paradigm shift" for how women with BV are treated. Clinicians will have to educate their patients on the role of sexual transmission, and male partners will need to accept their role in transmission and be willing to take both oral and topical medication.4
They also suggested similar studies are needed in more diverse populations, since racial and ethnic disparities in BV have been well-documented, and in women without regular male partners.4
"This trial provides data critical to educating clinicians and patients about the role of sexual transmission of bacterial vaginosis–associated bacteria and the benefit of male-partner treatment," Muzny and Sobel wrote.4 "It is time to start the conversation."
References:
1. Vodstrcil LA, Plummer EL, Fairley CK, et al. Male-partner treatment to prevent recurrence of bacterial vaginosis. N Engl J Med. 2025;392:947-957. doi:10.1056/NEJMoa2405404
2. CDC. Bacterial vaginosis (BV): About bacterial vaginosis (BV). https://www.cdc.gov/bacterial-vaginosis/about/index.html. Updated December 11, 2023. Accessed March 28, 2025.
3. New STI impacts 1 in 3 women: landmark study reveals men are the missing link. News release. Monash University. March 6, 2025. Accessed March 28, 2025. https://www.monash.edu/medicine/news/latest/2025-articles/new-sti-impacts-1-in-3-women-landmark-study-reveals-men-are-the-missing-link
4. Munzy CA, Sobel JD. Bacterial vaginosis — time to treat male partners. N Engl J Med. 2025;392:1026-1027. doi:10.1056/NEJMe2500373
